The Z-89 is a personal computer introduced in 1979 by Heathkit , but produced primarily by Zenith Data Systems (ZDS) in the early 1980s. It combined an updated version of the Heathkit H8 microcomputer and H19 terminal in a new case that also provided room for a built-in floppy disk on the right side of the display. Based on the Zilog Z80 microprocessor it is capable of running CP/M as well as Heathkit's own HDOS .
152-767: The Zenith Z-89 is based on the Zilog Z80 microprocessor running at 2.048 MHz, and supports the HDOS and CP/M operating systems. The US$ 2295 Z-89 is integrated in a terminal -like enclosure with a non-detachable keyboard, 12-inch monochrome CRT with a 80x25 character screen, 48 KB RAM , and a 5.25" floppy disk drive . The keyboard is of high build quality and has an unusual number of special purpose keys: REPEAT , ESC , Tab ↹ , CAPS , CTRL , SCROLL , RESET , BREAK , BACK SPACE , LINE FEED , DELETE , and three with white, red, and blue squares. There are five function keys and
304-601: A MOS Technology 8502 . Zilog was later producing a low-power Z80 suitable for the growing laptop computer market of the early 1980s. Intel produced a CMOS 8085 (80C85) used in battery-powered portable computers, such as the Kyocera -designed laptop from April 1983, also sold by Tandy (as TRS-80 Model 100 ), Olivetti, and NEC. In following years, however, CMOS versions of the Z80 (from both Zilog and Japanese manufacturers) would dominate this market as well, in products such as
456-422: A computer teaching kit which sold well at a very low price. Encouraged by this success, Sinclair renamed his company to Sinclair Research , and started looking to manufacture personal computers. Keeping the cost low was essential for Sinclair to avoid his products from becoming outpriced by American or Japanese equivalents as had happened to several of the previous Sinclair Radionics products. On 29 January 1980,
608-564: A golden handshake and an estimated £10,000 severance package. He had a former employee, Christopher Curry , establish a "corporate lifeboat" company named Science of Cambridge Ltd, in July 1977, called such as they were located near the University of Cambridge . By this time inexpensive microprocessors had started appearing on the market, which prompted Sinclair to start producing the MK14 ,
760-567: A ramdrive using a special driver (above the Z80's 64 KB memory limit) and a multi-serial card providing extra RS-232 ports. The 2 MHz Z80 could be upgraded to 4 MHz. In 1979, prior to Zenith's purchase of Heath Company , Heathkit designed and marketed this computer in kit form as the Heath H89 , assembled as the WH89, and without the floppy but with a cassette interface card as the H88 . (Prior to
912-712: A "blaze of publicity" at the Earl's Court Computer Show in London, and the ZX Microfair in Manchester . The ZX Spectrum was launched with two models: a 16KB 'basic' version, and an enhanced 48KB variant. The former model had an undercutting price of £125, significantly lower than its main competitor the BBC Micro , whilst the latter model's price of £175 was comparable to a third of an Apple II computer. Upon release,
1064-657: A 16-bit address register HL. In the 8080, this pairing was added to the BC and DE pairs as well, while HL was generalized to allow use as a 16-bit accumulator, not just an address register. The 8080 also introduced immediate 16-bit data for BC, DE, HL, and SP loads. Furthermore, direct 16-bit copying between HL and memory was now possible, using a direct address. The Z80 orthogonalized this further by making all 16-bit register pairs, including IX and IY, more general purpose, as well as allowing 16-bit copying directly to and from memory for all of these pairs. The 16-bit IX and IY registers in
1216-424: A Briton taking on the world, Sinclair has become the best-known name in micros." The media latched onto Sinclair's image; his "Uncle Clive" persona is said to have been created by the gossip columnist for Personal Computer World . The press praised Sinclair as a visionary genius, with The Sun lauding him as "the most prodigious inventor since Leonardo da Vinci ". Adamson and Kennedy wrote that Sinclair outgrew
1368-407: A byte and two T-states for each occurrence. This naturally makes the index register unavailable for any other use, or else the need to constantly reload it would negate its efficiency. ZX Spectrum The ZX Spectrum ( UK : / z ɛ d ɛ k s / ) is an 8-bit home computer developed and marketed by Sinclair Research . Considered one of the most influential computers ever made, it
1520-516: A command in BASIC, many keywords require a single keyboard stroke. Other keywords require a change of keyboard mode by a few keystrokes. The BASIC interpreter is derived from the one used on the ZX81 . A BASIC program for ZX81 can be entered into a ZX Spectrum with minimal modifications. However, Spectrum BASIC introduced numerous additional features, enhancing its usability. The ZX Spectrum character set
1672-405: A copyright on their assembly mnemonics, a new assembly syntax had to be developed for the Z80. This time a more systematic approach was used: These principles made it straightforward to find names and forms for all new Z80 instructions, as well as orthogonalizations of old ones, such as LD BC,1234 . Apart from naming differences, and despite a certain discrepancy in basic register structure,
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#17327915649431824-511: A custom interpreter made it possible to fit all of its functionality into a very small amount of read-only memory (ROM). The development process of the software was marked by disagreements between Nine Tiles and Sinclair Research. Sinclair placed an emphasis on expediting the release of the Spectrum, primarily by minimising alterations in the software from the ZX81, which had in turn been based on
1976-473: A day later, Faggin and Ungermann were kicking around ideas based on "integrated logic" when Ungermann said "how about Zilog?" Faggin immediately agreed, stating they could say it was the "last word in integrated logic". When they met the next day and both immediately recalled it, the company had its name. The first samples were returned from Mostek on March 9, 1976. By the end of the month, they had also completed an assembler -based development system . Some of
2128-689: A dedicated monitor , while application software is loaded and saved onto compact audio cassettes . The ZX Spectrum was initially distributed by mail order, but after severe backlogs it was sold through High Street chains in the United Kingdom. It was released in the US as the Timex Sinclair 2068 in 1983, and in some parts of Europe as the Timex Computer 2048 . Ultimately the Spectrum was released as seven different models, ranging from
2280-457: A full range of colour and sound for a price under $ 200. Although it was more enhanced than its British counterpart, sales proved poor and Timex Sinclair collapsed the following year. A crucial part of the company's marketing strategy was to implement regular price-cutting at strategic intervals to maintain market share . Ian Adamson and Richard Kennedy noted that Sinclair's method was driven by securing his leading position through "panicking"
2432-409: A fully hardware-based television raster generator with colour support. This enhancement indirectly provided the new machine with roughly four times the processing power of the ZX81, as the Z80 was relieved of video generation tasks. An initial ULA design flaw occasionally led to incorrect keyboard scanning, which was resolved by adding a small circuit board mounted upside down ("dead cockroach") next to
2584-603: A high of 40 per cent. Sales in the 1984 Christmas season were described as "extremely good". In early 1985 the British press reported the home computer boom to have ended, leaving many companies slashing prices of their hardware to anticipate lower sales. Despite this, celebration of Sinclair's success in the computing market continued at the Which Computer? show in Birmingham , where the five-millionth ZX Spectrum
2736-500: A high-level design, adding several concepts of his own. In particular, he used his experience on NEC minicomputers to add the concept of two sets of processor registers so they could quickly respond to interrupts . Ungerman began the development of a series of related controllers and peripheral chips that would complement the design. Through this period, Shima developed a legendary reputation for being able to convert logic concepts into physical design in realtime; while discussing
2888-630: A lacking distribution. Nigel Searle , the newly-appointed chief of Sinclair's computer division, said in June 1982 the company had no plans to stock the new machine in WHSmith , which was at the time Sinclair's only retailer. Searle explained that the mail-order system was in place due to there being no "obvious" retail outlets in the United Kingdom which could sell personal computers, and it made "better sense" financially to continue selling through mail-order. The company's conservative approach to distributing
3040-466: A low-cost product like this would not be able to compete with a design from a company with its own production lines, like Intel. They then began considering a more complex microprocessor instead, initially known as the Super 80, with the main feature being its use of a +5 V bus instead of the more common −5, +5 and 12 V used by designs like the 8080. The new design was intended to be compatible with
3192-458: A method using only the 8080-model registers. The Z80 also introduced a new signed overflow flag and complemented the fairly simple 16-bit arithmetics of the 8080 with dedicated instructions for signed 16-bit arithmetics. The 8080-compatible registers AF, BC, DE, HL are duplicated as a separate register file in the Z80, where the processor can quickly (four t-states, the least possible execution time for any Z80 instruction) switch from one bank to
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#17327915649433344-697: A non-textured surface were at risk of causing shock, and were asked to be sent back to a warehouse in Cambridgeshire which would supply a replacement within 48 hours. Development of the ZX Spectrum+ began in June 1984, and was released on 15 October that year at £179. It was assembled by AB Electronics in South Wales and Samsung in South Korea. This 48 KB Spectrum introduced a new QL -style case with an injection-moulded keyboard and
3496-459: A numeric keypad. The video display has reverse video and character graphics are available. The computer has two small card cages inside the cabinet on either side of the CRT, each of which accept up to three proprietary circuit cards. Upgrade cards available for this included disk controller cards (see below), a 16 KB RAM card that upgrades the standard 48 KB RAM to 64 KB, a RAM memory card accessible as
3648-431: A pivotal role in the early history of personal computing and video gaming , leaving an enduring legacy that influenced generations. Its introduction led to a boom in companies producing software and hardware , the effects of which are still seen. It was among the first home computers aimed at a mainstream audience, with some crediting it as responsible for launching the British information technology industry. The Spectrum
3800-460: A proposed feature, he would often interrupt and state how much room that would take on the chip and veto its addition if it was too large. The first pass at the design was complete by April 1975. Shima had completed a logic layout by the beginning of May. A second version of the logic design was issued on August 7 and the bus details by September 16. Tape-out was completed in November and converting
3952-422: A regular encoding (common with the 8080) is that each of the 8-bit registers can be loaded from themselves (e.g. LD A,A ). This is effectively a NOP . New block transfer instructions can move up to 64 kilobytes from memory to memory or between memory and I/O peripheral ports. Block instructions LDIR and LDDR ( l oa d , i ncrement/ d ecrement, r epeat) use HL to point to the source address, DE to
4104-506: A relative address ( JR instead of JP ) using a signed 8-bit displacement. Only the zero and carry flags can be tested for these new two-byte JR instructions. (All 8080 jumps and calls, conditional or not, are three-byte instructions.) A two-byte instruction specialized for program looping is also new to the Z80: DJNZ ( d ecrement j ump if n on- z ero) takes a signed 8-bit displacement as an immediate operand. The B register
4256-517: A reset button that functions as a switch shorting across the CPU reset capacitor. Electronically, it was identical to the previous 48 KB model. The machine outsold the rubber-key model two to one, however, some retailers reported a failure rate of up to 30%, compared with a more typical 5–6% for the older model. In early 1985, the original Spectrum was officially discontinued, and the ZX Spectrum+
4408-662: A significant commercial failure, selling only 17,000 units and losing Sinclair £7 million. It has since been described as "one of the great marketing bombs of postwar British industry". The ASA ordered Sinclair to withdraw advertisements for the C5 after finding that the company's claims about its safety could not be proved or justified. The combined failures of the C5 and QL caused investors to lose confidence in Sinclair's judgement. In May 1985, Sinclair Research announced their intention to raise an additional £10 to £15 million to restructure
4560-735: A significant drop in Sinclair's income from orders in January, as retailers were left with surplus stock. Subsequently, an upgraded model, the ZX Spectrum 128, was released in Spain in September 1985, with development financed by the Spanish distributor Investrónica. The launch of this model in the UK was postponed until January 1986 due to the substantial leftover inventory of the prior model. While
4712-552: A single chip, the essential hardware functions. Altwasser designed a graphics mode that required less than 7 kilobytes of memory and implemented it on the ULA. Vickers wrote most of the ROM code. Lengthy discussions between Altwasser and Sinclair engineers resulted in a broad agreement that the ZX Spectrum must have high-resolution graphics, 16 kilobytes of memory, an improved cassette interface , and an impressive colour palette. To achieve this,
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4864-517: A small office at 6 King's Parade , Cambridge. During early production, the machine was known as the ZX81 Colour or the ZX82 to highlight the machine's colour display, which differed from the black and white of its predecessors. The addendum "Spectrum" was added later on, to emphasise its 15-colour palette. Aside from a new crystal oscillator and extra chips to add additional kilobytes of memory,
5016-530: A system not using interrupts) it can be used as simply another 8-bit data register. The instructions LD A,R and LD A,I affect the Z80 flags register, unlike all the other LD (load) instructions. The Sign (bit 7) and Zero (bit 6) flags are set according to the data loaded from the Refresh or Interrupt source registers. For both instructions, the Parity/Overflow flag (bit 2) is set according to
5168-465: A television speaker. The ZX Spectrum +2 marked Amstrad's entry into the Spectrum market shortly after their acquisition of the Spectrum range and "Sinclair" brand in 1986. This machine featured a brand-new grey case with a spring-loaded keyboard, dual joystick ports, and an integrated cassette recorder known as the "Datacorder," akin to the Amstrad CPC 464 . However, it was largely identical to
5320-649: A time, was governed by the BASIC command 'BEEP', where programmers could manipulate parameters for pitch and duration. Furthermore, the processor remained occupied exclusively with the BASIC BEEPs until their completion, limiting concurrent operations. Despite these constraints, it marked a significant step forward from the ZX81 , which lacked any sound capabilities. Resourceful programmers swiftly devised workarounds; its rudimentary audio functionality compelled developers to explore unconventional methods such as programming
5472-502: A total of $ 10 million for the entire industry being spent in all of 1975 (equivalent to $ 57 million in 2023). Someone from Exxon contacted the still-unnamed company, and arranged a meeting that eventually led to them providing an initial $ 500,000 funding in June 1975 (equivalent to $ 2.8 million in 2023). With funding being discussed, and a design to be built, Shima joined in February 1975. Shima immediately set about producing
5624-428: A variable base address (as in recursive stack frames ) and can also reduce code size by removing the need for multiple short instructions using non-indexed registers. However, although they may save speed in some contexts when compared to long/complex "equivalent" sequences of simpler operations, they incur a lot of additional CPU time (e.g., 19 T-states to access one indexed memory location vs. as little as 11 to access
5776-475: A vehicle to advertise his inventions and buy components. In 1972, Sinclair had competed with Texas Instruments to produce the world's first pocket calculator , the Sinclair Executive . By the mid 1970s, Sinclair Radionics was producing handheld electronic calculators, miniature televisions, and the ill-fated digital Black Watch wristwatch. Due to financial losses, Sinclair sought investors from
5928-521: A week in order to meet the tight schedule given by the financial investors. The Z80 offered many improvements over the 8080: The Z80 took over from the 8080 and its offspring, the 8085 , in the processor market and became one of the most popular and widely used 8-bit CPUs. Some organizations such as British Telecom remained loyal to the 8085 for embedded applications, owing to their familiarity with it and to its on-chip serial interface and interrupt architecture. Likewise, Zenith Data Systems paired
6080-409: Is a Zilog Z80 , an 8-bit microprocessor , with a clock rate of 3.5 MHz . The original model Spectrum has 16 KB of ROM and either 16 kB or 48 kB of RAM. Video output is channelled through an RF modulator , intended for use with contemporary television sets, to provide a simple colour graphic display. Text is displayed using a grid of 32 columns × 24 rows of characters from
6232-679: Is also one of the best-selling British computers ever, with over five million units sold. It was released in the United Kingdom on 23 April 1982, and around the world in the following years, most notably in Europe, the United States, and Eastern Bloc countries. The machine was designed by English entrepreneur and inventor Sir Clive Sinclair and his small team in Cambridge , and was manufactured in Dundee , Scotland by Timex Corporation . It
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6384-553: Is decremented, and if the result is nonzero, then program execution jumps relative to PC; the flags remain unaltered. To perform an equivalent loop on an 8080 requires separate DEC and conditional jump (to a two-byte absolute address) instructions (totalling four bytes), and the DEC alters the flag register. The index register (IX/IY, often abbreviated XY) instructions can be useful for accessing data organised in fixed heterogenous structures (such as records ) or at fixed offsets relative
6536-510: Is in context unless carefully commented. Thus it is advisable that exchange instructions be used directly and in short discrete code segments. The Zilog Z280 instruction set includes JAF and JAR instructions which jump to a destination address if the alternate registers are in context (thus officially recognizing this programming complication). As on the 8080, 8-bit registers are typically paired to provide 16-bit versions. The 8080 compatible registers are: The new registers introduced with
6688-591: Is often referred to as the "alternate register set" (by some, the "primed" register file since the apostrophe character is used to denote them in assembler source code and the Zilog documentation). This emphasizes that only one set is addressable at any time. However, the 8-bit accumulator A with its flag register F is bifurcated from the "general purpose" register pairs HL, DE and BC. This is accomplished with two separate instructions used to swap their accessibilities: EX AF,AF' exchanges only register pair AF with AF', while
6840-557: Is one of the best-selling British computers of all time, retaining the title of Britain's top-selling computer until the Amstrad PCW surpassed it in the 1990s. It was discontinued in 1992. The ZX Spectrum was conceived and designed by engineers at Sinclair Research, founded by English entrepreneur and inventor Clive Sinclair , who was well known for his eccentricity and pioneering ethic. On 25 July 1961, three years after passing his A-levels , he founded Sinclair Radionics Ltd as
6992-535: Is significantly more advanced than the ZX81, with approximately four times faster average speeds. The original ZX Spectrum is remembered for its rubber chiclet keyboard , diminutive size and distinctive rainbow motif. It was originally released on 23 April 1982 with 16 KB of RAM for £125 (equivalent to £557 in 2023) or with 48 KB for £175 (equivalent to £780 in 2023); these prices were reduced to £99 (equivalent to £422 in 2023) and £129 (equivalent to £550 in 2023) respectively in 1983. Owners of
7144-511: Is the ZX81 , which lets it keep track of character positions on the TV screen by triggering an interrupt at wrap around (by connecting INT to A6). The interrupt vector register , I , is used for the Z80 specific mode 2 interrupts (selected by the IM 2 instruction). It supplies the high byte of the base address for a 128-entry table of service routine addresses which are selected via an index sent to
7296-414: Is used as the byte counter. The Z80 can input and output any register to an I/O port using register C to designate the port. (The 8080 only performs I/O through the accumulator A, using a direct port address specified in the instruction; a self-modifying code technique is required to use a variable 8080 port address.) The last group of block instructions perform a CP compare operation between
7448-564: The EXX instruction exchanges the three general purpose register pairs HL, DE and BC with their alternates HL', DE' and BC'. Thus the accumulator A can interact independently with any of the general purpose 8-bit registers in the alternate (or primed) register file, or, if HL' contains a pointer to memory, some byte there (DE' and BC' can also transfer 8-bit data between memory and accumulator A). This can become confusing for programmers because after executing EX AF,AF' or EXX what were previously
7600-445: The MIC port is intended for attachment to other audio devices as a line-in source. The ZX Spectrum integrated various design elements from the ZX81. The keyboard decoding and cassette interfaces were nearly identical, although the latter was programmed for higher-speed loading and saving. The central ULA integrated circuit shares some resemblance with that of the ZX81, but it features
7752-578: The AY-3-8912 chip, MIDI compatibility, an RS-232 serial port, an RGB monitor port, 32 KB of ROM including an improved BASIC editor, and an external keypad. The machine was simultaneously unveiled for the first time and launched in September 1985 at the SIMO '85 trade show in Spain, with a price of 44,250 pesetas . Sinclair later presented the ZX Spectrum 128 at The May Fair Hotel 's Crystal Rooms in London, where he acknowledged that entertainment
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#17327915649437904-536: The Advertising Standards Authority (ASA) in May of that year. Particularly serious were allegations that Sinclair was cashing cheques months before machines were shipped. By autumn 1984, Sinclair was still publicly forecasting that it would be a "million seller" and that 250,000 units would be sold by the end of the year. QL production was suspended in February 1985, and the price was halved by
8056-729: The Amstrad NC100 , Cambridge Z88 and Tandy's own WP-2. Perhaps a key to the initial success of the Z80 was the built-in DRAM refresh, at least in markets such as CP/M and other office and home computers. (Most Z80 embedded systems use static RAM that do not need refresh.) It may also have been its minimalistic two-level interrupt system, or conversely, its general multi-level daisy-chain interrupt system useful in servicing multiple Z80 IO chips. These features allowed systems to be built with less support hardware and simpler circuit board layouts. However, others claim that its popularity
8208-586: The CP/M operating system and Intel's PL/M compiler for 8080 (as well as its generated code), would run unmodified on the new Z80 CPU. Masatoshi Shima designed most of the microarchitecture as well as the gate and transistor levels of the Z80 CPU, assisted by a small number of engineers and layout people. CEO Federico Faggin was actually heavily involved in the chip layout work, together with two dedicated layout people. According to Faggin, he worked 80 hours
8360-529: The National Enterprise Board (NEB), who had bought a 43% interest in the company and streamlined his product line. Sinclair's relationship with the NEB had worsened, however, and by 1979 it opted to break up Sinclair Radionics entirely, selling off its television division to Binatone and its calculator division to ESL Bristol. After incurring a £7 million investment loss, Sinclair was given
8512-471: The ZX Spectrum character set , or from a custom set. The machine features a colour palette of 15 colours, consisting of seven saturated colours at two levels of brightness, along with black. The image resolution is 256×192 pixels, subject to the same colour limitations. To optimise memory usage, colour is stored separately from the pixel bitmap in a low resolution, 32×24 grid overlay, corresponding to
8664-581: The ZX80 home computer was launched to immediate popularity; notable for being one of the first computers available in the United Kingdom for less than £100. The company conducted no market research whatsoever prior to the launch of the ZX80; according to Sinclair, he "simply had a hunch" that the public was sufficiently interested to make such a project feasible and went ahead with ordering 100,000 sets of parts so that he could launch at high volume. On 5 March 1981,
8816-658: The ZX81 was launched worldwide to immense success with more than 1.5 million units sold, 60% of which was outside Britain. According to Ben Rosen , by pricing the ZX81 so low, the company had "opened up a completely new market among people who had never previously considered owning a computer". After its release, computing in Britain became an activity for the general public rather than the preserve of office workers and hobbyists. The ZX81's commercial success made Sinclair Research one of Britain's leading computer manufacturers, with Sinclair himself reportedly "amused and gratified" by
8968-469: The 16 KB model could purchase an internal 32 KB RAM upgrade, which for early "Issue 1" machines consisted of a daughterboard . Later issue machines required the fitting of 8 dynamic RAM chips and a few TTL chips. Users could mail their 16K Spectrums to Sinclair to be upgraded to 48 KB versions. Later revisions contained 64 KB of memory but were configured such that only 48 KB were usable. External 32 KB RAM packs that mounted in
9120-406: The 8080); the four remaining codes are used extensively as opcode prefixes : CB and ED enable extra instructions, and DD or FD select IX+d or IY+d respectively (in some cases without displacement d) in place of HL. This scheme gives the Z80 a large number of permutations of instructions and registers; Zilog categorizes these into 158 different "instruction types", 78 of which are the same as those of
9272-430: The 8080, as the Z80 sometimes indicates signed overflow where the 8080 would indicate parity, possibly causing the logic of some practical 8080 software to fail on the Z80. ) This new overflow flag is used for all new Z80-specific 16-bit operations ( ADC , SBC ) as well as for 8-bit arithmetic operations, while the 16-bit operations inherited from the 8080 ( ADD , INC , DEC ) do not affect it. Also, bit 1 of
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#17327915649439424-500: The 8080, but add many of the nice features of the Motorola 6800 , including index registers and improved interrupts . While still being set up, the industry newsletter Electronic News heard of them and published a story on the newly formed company. This attracted the attention of Exxon Enterprises, Exxon 's high-tech investment arm. At the time, in the midst of the recession, there was very little venture capital available, with
9576-676: The 8085 with the 16-bit Intel 8088 in its first MS-DOS computer, the Zenith Z-100 , despite having previous experience with its pioneering Z80-based Heathkit H89 and Zenith Z-89 products. However, other computers were made integrating the Z80 with other CPUs: the Radio Shack TRS-80 Model ;16 with a Motorola 68000 , the DEC Rainbow with an 8088, and the Commodore ;128 with
9728-464: The CPU during an interrupt acknowledge cycle; this index is simply the low byte part of the pointer to the tabulated indirect address pointing to the service routine. The pointer identifies a particular peripheral chip or peripheral function or event, where the chips are normally connected in a so-called daisy chain for priority resolution. Like the refresh register, this register has also sometimes been used creatively; in interrupt modes 0 and 1 (or in
9880-534: The CPU in Issue 1 ZX Spectrums. The machine's Sinclair BASIC interpreter is stored in 16 KiB ROM, along with essential system routines. The ROM code, responsible for tasks such as floating point calculations and expression parsing , exhibited significant similarities to ZX81, although a few outdated routines remained in the Spectrum ROM. The Spectrum's keyboard is imprinted with BASIC keywords. To input
10032-462: The Commodore 64 also employed colour attributes, it utilised a special multicolour mode and hardware sprites to circumvent attribute clash. Sound output is produced through a built-in beeper capable of generating a single channel with ten octaves. It is controlled by a single EAR bit. By toggling it on and off, simple sounds are generated. This speaker, capable of producing just one note at
10184-519: The Heath H89 as "the most professional looking" microcomputer available. Stating that the computer was "one of the finest" available for less than $ 3000, the magazine predicted that it "can have a major impact on the small computer market" if good software became available for it. BYTE wrote that the H89 "has a number of unique hardware features and the same excellent software support and documentation as
10336-464: The Intel 8080 (allowing operation of all 8080 programs on a Z80). The Zilog documentation further groups instructions into the following categories (most from the 8080, others entirely new like the block and bit instructions, and others 8080 instructions with more versatile addressing modes, like the 16-bit loads, I/O, rotates/shifts and relative jumps): No explicit multiply instructions are available in
10488-565: The ROM were also eliminated, rendering some older 48K and 128K games incompatible with the machine. The ZX Interface 1 was also rendered incompatible due to disparities in ROM and expansion connectors, making it impossible to connect and use the Microdrive units. Production of the +3 was discontinued in December 1990, reportedly in response to Amstrad's relaunch of their CPC range, with an estimated 15% of ZX Spectrums sold being +3 models at
10640-526: The Sinclair QL was in development, Sinclair also hoped to repeat his success with the Spectrum in the fledgling electric vehicle market, which he saw as ripe for a new approach. On 10 January 1985, Sinclair unveiled the Sinclair C5 , a small one-person battery electric recumbent tricycle . It marked the culmination of Sir Clive's long-running interest in electric vehicles. The C5 turned out to be
10792-472: The Spanish alphabet and show messages in Spanish. The appearance of the ZX Spectrum 128 is similar to the ZX Spectrum+, with the exception of a large external heatsink for the internal 7805 voltage regulator added to the right hand end of the case, replacing the internal heatsink in previous versions. This external heatsink led to the system's nickname, "The Toast Rack ". New features included 128 KB RAM with RAM disc commands, three-channel audio via
10944-422: The Spectrum's rubber keyboard was simplified from several hundred components to a conventional moving keyboard down to "four to five" moving parts using a new technology. The keyboard was still undergoing changes as late as February 1982; some sketches included a roundel-on-square key design which was later featured on the later Spectrum+ model. Dickinson recalled in 2007 that "everything was cost driven" and that
11096-461: The Z80 and 8086 syntax are virtually isomorphic for a large portion of instructions. Only quite superficial similarities (such as the word MOV, or the letter X, for extended register) exist between the 8080 and 8086 assembly languages, although 8080 programs can be translated to 8086 assembly language by translator programs . The Z80 uses 252 out of the available 256 codes as single byte opcodes ("root instruction" most of which are inherited from
11248-584: The Z80 are fairly conventional, ultimately based on the register structure of the Datapoint 2200 . The Z80 was designed as an extension of the Intel 8080, created by the same engineers, which in turn was an extension of the 8008 . The 8008 was basically a PMOS implementation of the TTL-based CPU of the Datapoint 2200. The 2200 design allowed 8-bit registers H and L (High and Low) to be paired into
11400-469: The Z80 are primarily intended as base address-registers, where a particular instruction supplies a constant offset that is added to the previous values, but they are also usable as 16-bit accumulators, among other things. A limitation is that all operand references involving IX or IY require an extra instruction prefix byte, adding at least four clock cycles over the timing of an instruction using HL instead; this sometimes makes using IX or IY less efficient than
11552-424: The Z80 are: The refresh register , R , increments each time the CPU fetches an opcode (or an opcode prefix, which internally executes like a 1-byte instruction) and has no simple relationship with program execution. This has sometimes been used to generate pseudorandom numbers in games, and also in software protection schemes. It has also been employed as a "hardware" counter in some designs; an example of this
11704-400: The Z80 had an alternate register set that duplicated them, two 16-bit index registers and additional instructions including bit manipulation and block copy/search. Initially intended for use in embedded systems like the 8080, the Z80's combination of compatibility, affordability, and superior performance propelled it to widespread adoption in video game systems and home computers during
11856-546: The Z80 in April 2024 after nearly five decades of production. At Fairchild Semiconductor , and later at Intel , physicist and engineer Federico Faggin had been working on fundamental transistor and semiconductor manufacturing technology. He also developed the basic design methodology used for memories and microprocessors at Intel and led the work on the Intel 4004 , the Intel 8080 and several other ICs. Masatoshi Shima
12008-455: The Z80 support and peripheral ICs were under development at this point, and many of them were launched during the following year. Among them were the Z80 CTC (counter/timer), Z80 DMA (direct memory access), Z80 DART (dual asynchronous receiver–transmitter), Z80 SIO (synchronous communication controller), and Z80 PIO (parallel input/output). The Z80 was officially launched in July 1976. One of
12160-470: The Z80. However, this would likely be erroneous code on the 8080, as DAA was defined for addition only on that processor. The Z80 has six new LD instructions that can load the DE, BC, and SP register pairs from memory, and load memory from these three register pairs—unlike the 8080. As on the 8080, load instructions do not affect the flags (except for the special-purpose I and R register loads). A result of
12312-520: The ZX Spectrum +3 power supply utilised a DIN connector and featured "Sinclair +3" branding on the case. Significant alterations caused a series of incompatibilities, such as the removal of several lines on the expansion bus edge connector. This resulted in complications for various peripheries. Additionally, changes in memory timing led to certain RAM banks being contended, causing failures in high-speed colour-changing effects. The keypad scanning routines from
12464-625: The ZX Spectrum 128 in most technical aspects. The machine retailed for £149. The new keyboard did not feature the BASIC keyword markings seen on earlier Spectrums, except for the keywords LOAD , CODE , and RUN , which were useful for loading software. Instead, the +2 introduced a menu system, almost identical to that of the ZX Spectrum 128, allowing users to switch between 48K BASIC programming with keywords and 128K BASIC programming, where all words, both keywords and others, needed to be typed out in full (though keywords were still stored internally as one character each). Despite these changes,
12616-482: The ZX Spectrum was intended to be, as quoted by Sinclair's marketing manager, essentially a "ZX81 with colour". According to Sinclair, the team also wanted to combine the ZX81's separate random-access memory sections for audio and video into a single bank. Chief engineer Richard Altwasser was responsible for the ZX Spectrum's hardware design. His main contribution was the design of the semi-custom uncommitted logic array (ULA) integrated circuit, which integrated, on
12768-529: The ZX80's software. The software architecture of the ZX80, however, had been tailored for a severely constrained memory system, and in Nine Tiles' opinion was unsuitable for the enhanced processing demands of the ZX Spectrum. Sinclair favoured solving this with expansion modules on the existing framework like with the ZX81, which Nine Tiles disagreed with. Ultimately, both designs were developed, but Vickers and Nine Tiles were unable to finish their version before
12920-621: The Zenith purchase, the Heathkit model numbers did not include the dash). Heath/Zenith also made a serial terminal, the H19 / Z-19 , based on the same enclosure (with a blank cover over the diskette drive cut-out) and terminal controller. The company offered an upgrade kit to convert the terminal into a full H89 / Z-89 computer. Another configuration, the Z-90 , changes the floppy drive controller from
13072-464: The alternate (primed) registers are now the main registers, and vice versa. The only way for the programmer to tell which set(s) are in context (while "playing computer" while scrutinizing the assembler source text, or worse, poring over code with a debugger) is to trace where each register swap is made at each point in the program. Obviously if many jump and calls are made within these code segments it can quickly become difficult to tell which register file
13224-407: The attention the machine received. Development of the ZX Spectrum began in September 1981, a few months after the release of the ZX81. Sinclair resolved to make his own products obsolete before his rivals developed the products that would do so. Parts of designs from the ZX80 and ZX81 were reused to ensure a speedy and cost-effective manufacturing process. The team consisted of 20 engineers housed in
13376-399: The beeper to emit multiple pitches. Later software became available that allowed for two-channel sound playback. The machine includes an expansion bus edge connector and 3.5 mm audio in/out ports, facilitating the connection of a cassette recorder for loading and saving programs and data. The EAR port has a higher output than the MIC and is recommended for headphones, while
13528-456: The byte at (HL) and the accumulator A. Register pair DE is not used. The repeating versions CPIR and CPDR only terminate if BC goes to zero or a match is found. HL is left pointing to the byte after ( CPIR ) or before ( CPDR ) the matching byte. If no match is found the Z ;flag is reset. There are non-repeating versions CPI and CPD . Unlike the 8080, the Z80 can jump to
13680-414: The case was to be more angular and wedge-like, in similar vein to an upgraded ZX81 model. Dickinson later settled on a flatter design with a raised rear section and rounded sides in order to depict the machine as "more advanced" as opposed to a mere upgrade. In drawing up potential logos, Dickinson proposed a series of different logotypes which all featured rainbow slashes across the keyboard. The design of
13832-422: The character cells. In practical terms, this means that all pixels within an 8x8 character block share one foreground colour and one background colour. Altwasser received a patent for this design. An "attribute" consists of a foreground and a background colour, a brightness level (normal or bright) and a flashing "flag" which, when set, causes the two colours to swap at regular intervals. This scheme leads to what
13984-551: The company sold their entire computer product range, along with the "Sinclair" brand name, to Alan Sugar 's Amstrad for £5 million. The takeover sent ripples through the London Stock Exchange , but Amstrad's shares soon recovered, with one stock broker affirming that " the City appears to have taken the news in its stride". Amstrad's acquisition of the brand name saw the release of three ZX Spectrum models throughout
14136-408: The company's Dryburgh factory. Prior to the manufacture of the ZX81, however, Timex had little experience in assembling electronics and had not originally been an obvious choice of manufacturing subcontractor. It was a well-established manufacturer of mechanical watches but was facing a crisis at the beginning of the 1980s; profits had dwindled to virtually zero as the market for watches stagnated in
14288-411: The company. Clive Sinclair became a focal point during the ZX Spectrum's marketing campaign by putting a human face onto the business. Sinclair Research was portrayed in the media as a "plucky" British challenger taking on the technical and marketing might of giant American and Japanese corporations. As David O'Reilly noted in 1986, "by astute use of public relations, particularly playing up his image of
14440-468: The competition. While most companies at the time reduced prices of their products while their market share was dwindling, Sinclair Research discounted theirs shortly after sales had peaked, throwing the competition into "utter disarray". Sinclair Research made a profit of £14 million in 1983, compared to £8.5 million the previous year. Turnover doubled from £27.2 million to £54.5 million, which equated to roughly £1 million for each person employed directly by
14592-502: The current state of the IFF2 flip-flop. Although the Z80 is generally considered an eight-bit CPU, it has a four-bit ALU , so calculations are done in two steps. The first Intel 8008 assembly language was based on a very simple (but systematic) syntax inherited from the Datapoint 2200 design. This original syntax was later transformed into a new, somewhat more traditional, assembly language form for this same original 8008 chip. At about
14744-404: The data transfer speed, the team significantly decreased the length of tones that represent binary data. To increase the reliability, a leading period of constant tone was introduced, which allowed the cassette recorder's automatic gain control to settle itself down, eliminating hisses on the tape. A Schmitt trigger was added inside the ULA to reduce noise of the received signal. Originally,
14896-415: The design directly. Faggin thought this would mean they could never compete even if they set up their own lines, and the agreement fell through. He then turned to Mostek, who agreed to a term of exclusivity while Zilog got their lines set up, and were eventually given the second source agreement. After considering many names for the new company, and finding them so unmemorable they could not recall them even
15048-482: The design. Sometime later, Shima was told by an engineer within NEC that the traps had delayed their copying efforts by six months. The successful launch allowed Faggin and Ungermann to approach Exxon looking for funding to build their own fab. The company agreed, and Zilog built a production line very rapidly. This allowed them to capture about 60 to 70% of the total market for Z80 sales. With their own line running, Mostek
15200-571: The destination address, and BC as a byte counter. Bytes are copied from source to destination, the pointers are incremented or decremented, and the byte counter is decremented until BC reaches zero. Non-repeating versions LDI and LDD move a single byte and bump the pointers and byte counter, which if it becomes zero resets the P/V ;flag. Corresponding memory-to-I/O instructions INIR , INDR , OTIR , OTDR , INI , IND , OUTI and OUTD operate similarly, except that B, not BC,
15352-526: The direction of Les Vadasz, further diluting the microprocessor's place in the company. That year, the 1973–1975 recession reached a peak and Intel laid off a number of employees. All of this led to Faggin becoming restless, and he invited Ungermann out for drinks and asked if he would be interested in starting their own company. Ungermann immediately agreed, and as he had less to do at Intel, left in August or September, followed by Faggin, whose last day at Intel
15504-428: The end of that month. Supply did not return to normal until the 1982 Christmas season, however. Production of the machine rapidly increased with the arrival of the more inexpensive Issue 2 motherboard , a redesign of the main circuit board which addressed hardware manufacturing defects that affected production of the first model. Sales of the ZX Spectrum reached 200,000 in its first nine months, rising to 300,000 for
15656-623: The end of the year. It ultimately flopped, with 139,454 units being manufactured. The ZX Spectrum+, a rebranded ZX Spectrum with identical technical specifications except for the QL-like keyboard, was introduced in October 1984 and made available in WHSmith's stores the day after its launch. Retailers stocked the device in high quantities, anticipating robust Christmas sales. Nevertheless, the product did not perform as well as projected, leading to
15808-514: The entry level with 16 KB RAM released in 1982 to the ZX ;Spectrum +3 with 128 KB RAM and built-in floppy disk drive in 1987. Throughout its life, the machine primarily competed with the Commodore 64 , BBC Micro , Dragon 32 , and the Amstrad ;CPC range. Over 24,000 different software products were released for the ZX Spectrum. The Spectrum played
15960-540: The face of competition from the digital and quartz watches . Recognising the trend, Timex's director, Fred Olsen , determined that the company would diversify into other areas and signed a contract with Sinclair. The ZX Spectrum was officially revealed before journalists by Sinclair at the Churchill Hotel in Marylebone , London, on 23 April 1982. Later that week, the machine was officially presented in
16112-486: The first customers was a buyer who, unknown to Zilog, worked for NEC. At the time, the Japanese electronics companies were well known for taking US chip designs and producing them without a license. The Zilog team had worried about this, and Faggin had come up with the idea of adding transistors that would be subtly modified to operate differently than a visual inspection would suggest. Shima added six of these "traps" around
16264-513: The flags register (a spare bit on the 8080) is used as a flag N that indicates whether the last arithmetic instruction executed was a subtraction or addition. The Z80 version of the DAA instruction (decimal adjust accumulator for BCD arithmetic) checks the N ;flag and behaves accordingly, so a (hypothetical) subtraction followed later by DAA will yield a different result on an old 8080 than on
16416-449: The hard-sectored controller (max 100 kB) to a soft-sectored controller that supported double-sided , double density, 96 tpi drives with a capacity of 640 kB. It also came standard with 64 KB of RAM. There were several external drive systems available for the H89 / Z-89 . A maximum of two disk controller cards can be installed in a standard system. Creative Computing described
16568-631: The introductory 2.5 MHz , via the well known 4 MHz (Z80A), up to 6 MHz (Z80B) and 8 MHz (Z80H). The NMOS version has been produced as a 10 MHz part since the late 1980s. CMOS versions were developed with specified upper frequency limits ranging from 4 MHz up to 20 MHz for the version sold today. The CMOS versions allowed low-power standby with internal state retained, having no lower frequency limit. The fully compatible derivatives HD64180 / Z180 and eZ80 are currently specified for up to 33 MHz and 50 MHz, respectively. The programming model and register set of
16720-428: The keyboard surprised many users due to its use of rubber keys, described as offering the feel of "dead flesh". Sinclair himself remarked that the keyboard's rubber mould was "unusual", but consumers were undeterred. Despite very high demand, Sinclair Research was "notoriously late" in delivering the ZX Spectrum. Their practice of offering mail-order sales before units were ready ensured a constant cash flow, but meant
16872-661: The late 1970s and early 1980s, fueling the personal computing revolution. Products it was used in include the Osborne 1 , Radio Shack TRS-80 , ColecoVision , ZX Spectrum and the Pac-Man cabinet; in later years it remained used in portables, best known for use in the Game Boy and TI-83 series . The Z80 was the brainchild of Federico Faggin , a key figure behind the creation of the Intel 8080. After leaving Intel in 1974, Faggin co-founded Zilog with Ralph Ungermann . The Z80
17024-433: The late 1980s, each with varying improvements. By 1990, Sinclair Research consisted of Sinclair and two other employees down from 130 employees at its peak in 1985. The ZX Spectrum was officially discontinued in 1992, after ten years on the market. Sinclair Research thereafter continued to exist as a one-man company, marketing Sir Clive Sinclair's inventions until his death in September 2021. The central processing unit
17176-443: The launch of the Spectrum and it was not used. The distinctive case and colourful design of the ZX Spectrum was the creation of Rick Dickinson , a young British industrial designer who had been hired by Sinclair to design the ZX81. Dickinson was tasked to design a sleeker and more "marketable" appearance to the new machine, whilst ensuring all 192 BASIC functions could fit onto 40 physical keys. Early sketches from August 1981 showed
17328-412: The layout remained identical to that of the 128. The ZX Spectrum +3 , which was launched in 1987, bore a resemblance to its predecessor but introduced a built-in 3-inch floppy disk drive instead of the cassette drive. Initially priced at £249, it later retailed for £199. It was the only Spectrum model capable of running the CP/M operating system without additional hardware. Unlike its predecessors,
17480-500: The machine into 48K mode, keeping the current BASIC program intact (although there is no command to switch back to 128K mode). To enable BASIC programmers to access the additional memory, a RAM disk was created where files could be stored in the additional 80 KB of RAM. The new commands took the place of two existing user-defined-character spaces causing compatibility problems with certain BASIC programs. Unlike its predecessors, it has no internal speaker, and can only produce sound from
17632-469: The machine was criticised, with disillusioned customers telephoning and writing letters. Demand sky-rocketed beyond Sinclair's planned 20,000 monthly unit output to a backlog of 30,000 orders by July 1982. Due to a scheduled holiday at the Timex factory that summer, the backlog had risen to 40,000 units. Sinclair issued a public apology in September that year, and promised that the backlog would be cleared by
17784-474: The minimalist, Bauhaus approach to the Spectrum gave it an elegant yet "[non] revolutionary" form. The drawing board on which Dickinson designed the ZX Spectrum is now on display in the Science Museum in London. The need for an improved cassette interface was apparent from the number of complaints received from ZX81 users, who encountered problems when trying to save and load programs. To increase
17936-414: The new memory would be available as eight pages of 16 KB at the top of the address space. The same technique was used to page between the new 16 KB editor ROM and the original 16 KB BASIC ROM at the bottom of the address space. The new sound chip and MIDI out abilities were exposed to the BASIC programming language with the command PLAY and a new command SPECTRUM was added to switch
18088-399: The organisation. Given the loss of confidence in the company, securing the funds proved to be a challenging task. In June 1985, business magnate Robert Maxwell disclosed a takeover bid for Sinclair Research through Hollis Brothers, a subsidiary of his Pergamon Press . However, the deal was terminated in August 1985. The future of Sinclair Research remained uncertain until 7 April 1986, when
18240-403: The original H-8 system". Zilog Z80 The Zilog Z80 is an 8-bit microprocessor designed by Zilog that played an important role in the evolution of early computing. Launched in 1976 and software-compatible with the Intel 8080 , it offered a compelling alternative due to its better integration and increased performance. As well as the 8080's seven registers and flags register,
18392-426: The original Z80 (being 1 clock slower than in the 8080/8085); nonetheless, they are about twice as fast as performing the same calculations using 8-bit operations, and equally important, they reduce register usage. It was not uncommon for programmers to "poke" different offset displacement bytes (which were typically calculated dynamically) into indexed instructions; this is an example of self-modifying code , which
18544-407: The original Z80, though registers A and HL can be multiplied by powers of two with ADD A,A and ADD HL,HL instructions (similarly IX and IY also). Shift instructions can also multiply or divide by powers of two. Different sizes and variants of additions, shifts, and rotates have somewhat differing effects on flags because most of the flag-changing properties of the 8080 were copied. However,
18696-483: The other; a feature useful for speeding up responses to single-level, high-priority interrupts. A similar feature was present in the 2200, but was never implemented at Intel. The dual register-set is very useful in the embedded role, as it improves interrupt handling performance, but found widespread use in the personal computer role as an additional set of general registers for complex code like floating-point arithmetic or home computer games. The duplicate register file
18848-418: The parity flag bit P of the 8080 (bit 2) is called P/V (parity/overflow) in the Z80 as it serves the additional purpose of a twos complement overflow indicator, a feature lacking in the 8080. Arithmetic instructions on the Z80 set it to indicate overflow rather than parity, while bitwise instructions still use it as a parity flag. (This introduces a subtle incompatibility of the Z80 with code written for
19000-475: The rear expansion slot were available from third parties. Both machines had 16 KB of onboard ROM. An "Issue 1" ZX Spectrum can be distinguished from Issue 2 or 3 models by the colour of the keys – light grey for Issue 1, blue-grey for later machines. Although the official service manual states that approximately 26,000 of these original boards were manufactured, subsequent serial number analysis shows that only 16,000 were produced, almost all of which fell in
19152-463: The role of microcomputer manufacturer and "accepted the mantle of pioneering boffin leading Britain into a technological utopia". Sinclair's contribution to the technology sector resulted in him being knighted upon the recommendation of Margaret Thatcher in the Queen's 1983 Birthday Honours List . The United Kingdom was largely immunised from the effects of the video game crash of 1983 , due to
19304-535: The same memory using HL and INC to point to the next). Thus, for simple or linear accesses of data, use of IX and IY tend to be slower and occupy more memory. Still, they may be useful in cases where the "main" registers are all occupied, by removing the need to save/restore registers. Their officially undocumented 8-bit halves (see below) can be especially useful in this context, for they incur less slowdown than their 16-bit parents. Similarly, instructions for 16-bit additions are not particularly fast (11 clocks) in
19456-517: The same time, the new assembly language was also extended to accommodate the additional addressing modes in the more advanced Intel 8080 chip (the 8008 and 8080 shared a language subset without being binary compatible ; however, the 8008 was binary compatible with the Datapoint 2200). In this process, the mnemonic L , for LOAD , was replaced by various abbreviations of the words LOAD , STORE and MOVE , intermixed with other symbolic letters. The mnemonic letter M , for memory (referenced by HL),
19608-519: The saturation of home computers such as the ZX Spectrum. The microcomputer market continued to grow and game development was unhindered despite the turbulence in the American markets. Indeed, computer games remained the dominant sector of the British home video game market up until they were surpassed by Sega and Nintendo consoles in 1991. By the end of 1983 there were more than 450 companies in Britain selling video games on cassette, compared to 95
19760-540: The serial number range 001-000001 to 001-016000. An online tool now exists to allow users to ascertain the likely issue number of their ZX Spectrum by inputting the serial number. These models experienced numerous changes to its motherboard design throughout its life; mainly to improve manufacturing efficiencies, but also to correct bugs from previous boards. Another issue was with the Spectrum's power supply. In March 1983, Sinclair issued an urgent recall warning for all owners of models bought after 1 January 1983. Plugs with
19912-462: The system took up slightly less than 7 kilobytes of memory, leaving an additional 9 kilobytes to write programs — a figure that pleased the team. Much of the firmware was written by computer scientist Steve Vickers from Nine Tiles, who compiled all control routines to produce the Sinclair BASIC interpreter, a custom variant of the general purpose BASIC programming language. Making
20064-438: The tape into a production mask required two more months. Faggin had already started looking for a production partner. By this time, Synertek and Mostek had both set up the depletion-mode production lines that could be used to produce the design. Having talked to Synertek previously, Faggin approached them first. However, the president of Synertek demanded that the company be given a second source license, allowing them to sell
20216-440: The team aimed for data transfer speed of 1000 baud , but succeeded in getting it to work at a considerably faster 1500 baud. Unlike the ZX81, the Spectrum was able to maintain its display during loading and saving operations, and programmers took advantage of this to show a splash screen whilst loading took place in the background. As with the ZX81, the ZX Spectrum was manufactured in Dundee , Scotland, by Timex Corporation at
20368-409: The team had to divorce the central processing unit (CPU) away from the main display to enable it to work at full efficiency – a method which contrasted with the ZX81's integrated CPU. The inclusion of colour to the display proved a major obstacle to the engineers. A Teletext -like approach was briefly considered, in which each line of text would have colour-change codes inserted into it. However, this
20520-409: The value should be used as a memory address (as mentioned below), while the 8086 syntax uses brackets instead of ordinary parentheses for this purpose. Both Z80 and 8086 use the + sign to indicate that a constant is added to a base register to form an address. Note that the 8086 is not a complete superset of the Z80. BX is the only 8086 register pair that can be used as a pointer. Because Intel claimed
20672-419: The whole of the first year. By August 1983 total sales in Britain and Europe had exceeded 500,000, with the millionth Spectrum manufactured on 9 December 1983. By this point, an average of 50,000 units were being purchased each month. In July 1983, the ZX Spectrum was launched in the United States as the more enhanced Timex Sinclair 2068 . Advertisements described it as offering 72 kilobytes of memory, having
20824-418: The world market since large companies like NEC , Toshiba , Sharp , and Hitachi started to manufacture the device (or their own Z80-compatible clones or designs). The Z80 continued to be used in embedded systems for decades after its introduction, with ongoing advancements. The latest addition to the Z80 family is the eZ80 , which was offered alongside successor chips. Zilog announced the discontinuation of
20976-402: The year before. An estimated 10,000 to 50,000 people, mostly young men, were developing games out of their homes based on advertisements in popular magazines. The growth of video games during this period has been compared to the punk subculture , fuelled by young people making money from their games. By the mid 1980s, Sinclair Research's share of the British home computer market had climbed to
21128-407: Was Halloween 1974. When Shima heard, he asked to come to the new company as well, but having no actual product design or money, they told him to wait. The newly formed and unnamed company initially began designing a single-chip microcontroller called the 2001. They met with Synertek to discuss fabrication on their lines, and when Faggin began to understand the costs involved it became clear that
21280-499: Was dubbed "colour clash" or attribute clash , where a desired colour of a specific pixel could not be selected, but only the colour attributes of an 8x8 block. This became a distinctive feature of the Spectrum, requiring programs, especially games, to be designed with this limitation in mind. In contrast, other machines available at the same time, such as the Amstrad CPC or the Commodore 64 , did not suffer from this limitation. While
21432-454: Was due to the duplicated registers that allowed fast context switches or more efficient processing of things like floating-point math compared to 8-bit CPUs with fewer registers. (The Z80 can keep several such numbers internally, using HL'HL, DE'DE and BC'BC as 32-bits registers, avoiding having to access them from slower RAM during computation.) For the original NMOS design, the specified upper clock-frequency limit increased successively from
21584-428: Was expanded compared to that of the ZX81, which lacked lowercase letters. Spectrum BASIC incorporated extra keywords for better graphics and sound functionality, and support for multi-statement lines was added. The built-in ROM tape modulation software routines for cassette data storage enable data transfers at an average speed of 171 bits per second (bit/s), with a theoretical peak speed of 256 bit/s. The tape modulation
21736-460: Was given the go-ahead to start sales of their own versions, the MK3880, which provided a second-source for customers which Intel lacked. At the time, a second-source was considered extremely important as a start-up like Zilog might go out of business and leave potential customers stranded. Faggin designed the instruction set to be binary compatible with the 8080 so that most 8080 code, notably
21888-604: Was issued as a prize. The ZX Spectrum's successor, the Sinclair QL , was officially announced on 12 January 1984, shortly before the Apple Macintosh went on sale. Contrasting with its predecessors, the QL was aimed at more serious, professional home users. It suffered from several design flaws; fully operational QLs were not available until the late summer, and complaints against Sinclair concerning delays were upheld by
22040-546: Was lifted out from within the instruction mnemonic to become a syntactically freestanding operand , while registers and combinations of registers became very inconsistently denoted; either by abbreviated operands (MVI D, LXI H and so on), within the instruction mnemonic itself (LDA, LHLD and so on), or both at the same time (LDAX B, STAX D and so on). Illustration of four syntaxes, using samples of equivalent, or (for 8086) very similar, load and store instructions. The Z80 syntax uses parentheses around an expression to indicate that
22192-403: Was made to be small, simple, and most importantly inexpensive, with as few components as possible. The addendum "Spectrum" was chosen to highlight the machine's colour display, which differed from the black-and-white display of its predecessor, the ZX81 . Rick Dickinson designed its distinctive case, rainbow motif, and rubber keyboard . Video output is transmitted to a television set rather than
22344-449: Was reduced in price to £129. In 1985, Sinclair developed the ZX Spectrum 128 (codenamed Derby ) in conjunction with their Spanish distributor Investrónica (a subsidiary of El Corte Inglés department store group). Investrónica had helped adapt the ZX Spectrum+ to the Spanish market after their government introduced a special tax on all computers with 64 KB RAM or less, and a law which obliged all computers sold in Spain to support
22496-531: Was regular practice on nearly all early 8-bit processors with non- pipelined execution units. The index registers have a parallel instruction to JP (HL) , which is JP (XY) . This is often seen in stack-oriented languages like Forth , which at the end of every Forth word (atomic subroutines comprising the language) must jump unconditionally back to their thread interpreter routines. Typically this jump instruction appears many hundreds of times in an application, and using JP (XY) rather than JP THREAD saves
22648-467: Was released in July 1976. With the revenue from the Z80, the company built its own chip factories . Zilog licensed the Z80 to the US-based Synertek and Mostek , which had helped them with initial production, as well as to a European second-source manufacturer SGS . The design was also copied by several Japanese, Eastern European and Soviet manufacturers. This won the Z80 acceptance in
22800-470: Was ruled out, as it was deemed unsuitable for high-resolution graphs or diagrams that involved multiple colour changes. Altwasser devised the idea of allocating a colour attribute to each character position on the screen. This ultimately used eight bits of memory for each character position; three bits to provide any one of eight foreground colours and three bits for the eight background colours , one bit for extra brightness and one bit for flashing. Overall,
22952-421: Was the most common use of home computers. Due to the large number of unsold Spectrum+ models, Sinclair decided not to start it selling in the United Kingdom until January 1986 at a price of £179. The Zilog Z80 processor used in the Spectrum has a 16-bit address bus, which means only 64 KB of memory can be directly addressed. To facilitate the extra 80 KB of RAM the designers used bank switching so
23104-430: Was the principal logic and transistor-level designer of the 4004 and the 8080 under Faggin's supervision, while Ralph Ungermann was in charge of custom integrated circuit design. In early 1974, Intel viewed their microprocessors not so much as products to be sold on their own but as a way to sell more of their main products, static RAM and ROM . A reorganization placed many of the formerly independent sections under
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