120-436: The Cambridge Z88 is a Z80 -based notebook computer released in 1987 by Cambridge Computer , the company formed for this purpose by Clive Sinclair . It was approximately A4 paper sized and lightweight at 0.9 kg (2.0 lb), running on four AA batteries for 20 hours of use. It was packaged with a built-in combined word processing / spreadsheet / database application called PipeDream (functionally equivalent to
240-701: A Cromemco Z-2 with iCom 8-inch soft-sectored floppy disk drives"; he also owned a TRS-80 Model I , and the first subject discussed in the column was an add-on that permitted it to use the same data and CP/M applications as the Cromemco. The next column appeared in December 1980 with the subtitle "BASIC, Computer Languages, and Computer Adventures"; Ezekiel II, a Compupro S-100 CP/M system, debuted in March 1983. Other computers received nicknames, such as Zorro , Pournelle's "colorful" Zenith Z-100 , and Lucy Van Pelt ,
360-601: 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
480-459: A Ph.D. in political science in March 1964. His master's thesis is titled "Behavioural observations of the effects of personality needs and leadership in small discussion groups", and is dated 1957. Pournelle's Ph.D. dissertation is titled "The American political continuum; an examination of the validity of the left-right model as an instrument for studying contemporary American political 'isms'". Pournelle married Roberta Jane Isdell in 1959;
600-453: A "fussbudget" IBM PC ; he referred to generic PC compatibles as "PClones". Pournelle often denounced companies that announced vaporware , sarcastically writing that they would arrive " Real Soon Now " (later abbreviated to just "RSN"), and those that used software copy protection . As part of a redesign in June 1984, the magazine renamed the popular column to "Computing at Chaos Manor", and
720-657: 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
840-469: A 1987 BBC Micro ROM called Acornsoft View Professional), along with several other applications and utilities, such as a Z80-version of the BBC BASIC programming language . The Z88 evolved from Sir Clive Sinclair 's Pandora portable computer project which had been under development at Sinclair Research during the mid-1980s. Following the sale of Sinclair Research to Amstrad , Sinclair released
960-582: A 1997 article, Norman Spinrad wrote that Pournelle had written the SDI portion of Ronald Reagan 's State of the Union Address , as part of a plan to use SDI to get more money for space exploration using the larger defense budget. Pournelle wrote in response that while the Citizens' Advisory Council on National Space Policy "wrote parts of Reagan's 1983 SDI speech, and provided much of the background for
1080-476: 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 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
1200-454: A built-in eight-line, 64 × 640 pixel super-twisted nematic display which has greater contrast than conventional twisted nematic LCDs. The 64 kB addressable by the Z80 processor are divided in four banks of 16 kB each. The maximum memory of 4 MiB for the system is also divided in 256 segments of 16 kB each. The hardware can map any of the 16 kB blocks to any of the four banks. The first 512 kB are reserved for ROM;
1320-456: 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. Jerry Pournelle Jerry Eugene Pournelle ( / p ʊər ˈ n ɛ l / ; August 7, 1933 – September 8, 2017) was an American scientist in the area of operations research and human factors research , a science fiction writer, essayist, journalist, and one of
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#17327934219851440-669: A collection of links. In his book Dave Barry in Cyberspace , humorist Dave Barry has fun with Pournelle's guru column in Byte magazine. Pournelle, in collaboration with his wife, Roberta (who was an expert on reading education) wrote the commercial education software program called Reading: The Learning Connection. Pournelle served as campaign research director for the mayoral campaign of 1969 for Los Angeles Mayor Sam Yorty (Democrat), working under campaign director Henry Salvatori . The election took place on May 27, 1969. Pournelle
1560-533: A college-undergraduate assistant and up to myself. (Not that I'm the last word in sophistication, but I do sit here and pound this machine a lot; if I can't get something to work, it takes an expert.) Fair warning, then: the very nature of this column limits its scope. I can't talk about anything I can't run on my machines, nor am I likely to discuss things I have no use for. Among recurring characters were Pournelle's family members, friends, and many computers. He introduced to readers "my friend Ezekiel, who happens to be
1680-689: A computer to write in 1977 on the advice of his "mad" friend Dan MacLean. He wrote the "Computing at Chaos Manor" column in Byte , describing experiences with computer hardware and software, some purchased and some sent by vendors for review, at his home office. Because Pournelle was then, according to the magazine, "virtually Byte ' s only writer who was a mere user—he didn't create compilers and computers, he merely used them", it began as "The User's Column" in July 1980. Subtitled "Omikron TRS-80 Boards, NEWDOS+, and Sundry Other Matters", an Editor's Note accompanied
1800-405: 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,
1920-473: 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
2040-553: A fruitful collaboration with Larry Niven ; he has also collaborated on novels with Roland J. Green , Michael F. Flynn , and Steven Barnes , and collaborated as an editor on an anthology series The Endless Frontier with John F. Carr . In 2010, his daughter Jennifer R. Pournelle (writing as J.R. Pournelle), an archaeology professor, e-published a novel Outies , an authorized sequel to the Mote in God's Eye series. Pournelle began using
2160-527: A government job for Pournelle's son, Richard. At the time, Pournelle and Gingrich were reported to be collaborating on "a science fiction political thriller." Pournelle's relationship with Gingrich was long established even then, as Pournelle had written the preface to Gingrich's book, Window of Opportunity (1985). Years after Byte shuttered, Pournelle wrote his Chaos Manor column online. He reprised it at Byte.com, which he helped launch with journalist Gina Smith , John C. Dvorak , and others. However, after
2280-500: 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
2400-627: A history of computing. A memorable column in August 1989 was "The Great Power Spike", which gives a digital necropsy of his electronic equipment after high voltage transmission wires dropped onto the power line for his neighborhood. After the print version of Byte ended publication in the United States, Pournelle continued publishing the column for the online version and international print editions of Byte . In July 2006, Pournelle and Byte declined to renew their contract and Pournelle moved
2520-466: 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
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#17327934219852640-463: A low-power CMOS version of the popular Zilog Z80 microprocessor . It comes with 32 kB of internal pseudo-static RAM and 128 kB of ROM containing the operating system (called OZ ). The memory can be expanded up to 3.5 MB of RAM, the contents of which are preserved across sessions. An integrated capacitor prevents the Z88 from losing its data for the limited time it takes to change
2760-458: 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
2880-671: A number of years was a high church Anglican , in part because Anglican theology was virtually identical to Catholic theology , with the exception that the Anglicans accepted as moral the use of birth control. Pournelle eventually returned to the Catholic Church, as his other beliefs were consistent with the Catholic communion, although he did not agree with the Church's position on birth control. Despite his estrangement from
3000-611: A pro- Vietnam War advertisement in Galaxy Science Fiction . During the 1970s and 1980s, he also published articles on military tactics and war gaming in the military simulations industry in Avalon Hill 's magazine The General . That led him into correspondences with some of the early figures in Dungeons & Dragons and other fantasy role-playing games. Two of his collaborations with Larry Niven reached
3120-460: 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
3240-422: 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
3360-506: 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
3480-684: A semi-regular (i.e.: every 2 to 3 months) basis, which would cover the wild microcomputer goings-on at the Pournelle House ("Chaos Manor") in Southern California. We said yes. Herewith the first installment ... Pournelle stated that This will be a column by and for computer users, and with rare exceptions I won't discuss anything I haven't installed and implemented here in Chaos Manor. At Chaos Manor we have computer users ranging in sophistication from my 9-year-old through
3600-413: A sequel to Space Viking but abandoned this in the early 1990s, however John F. Carr and Mike Robertson completed this sequel, entitled The Last Space Viking , and it was published in 2011. In 2013, Variety reported that motion picture rights to Pournelle's novel Janissaries had been acquired by the newly formed Goddard Film Group, headed by Gary Goddard . The IMDb website reported that
3720-502: A shakeup, he announced that rather than stay at United Business Media, he would follow Smith, Dvorak, and 14 other news journalists to start an independent tech and politics site called anewdomain.net. As an active director of that site and others it launched, Pournelle wrote, edited, and worked with young writers and journalists on the craft of writing about science and tech. Beginning during his tenure at Boeing Company, Pournelle submitted science fiction short stories to John W. Campbell ,
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3840-530: 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
3960-469: A term as President of the Science Fiction and Fantasy Writers of America . Pournelle's journalism focused primarily on the computer industry, astronomy, and space exploration. From the 1970s until the early 1990s, he contributed to the computer magazine Byte , writing from the viewpoint of an intelligent user, with the oft-cited credo, "We do this stuff so you won't have to." He created one of
4080-751: A textbook at the United States Military Academy (West Point), the United States Air Force Academy (Colorado Springs), the Air War College , and the National War College . He told fellow author Robert Heinlein , Pournelle recalled, "that once I got into advance plans at Boeing I probably wrote more science fiction than he did, and I didn't have to put characters in mine". In the late 1950s, while conducting operations research at
4200-502: 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
4320-428: 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
4440-431: A website with a daily online journal, "View from Chaos Manor," a blog dating from before the use of that term. It is a collection of his "Views" and "Mail" from a large variety of readers. This is a continuation of his 1980s blog-like online journal on GEnie . He said he resists using the term "blog" because he considered the word ugly, and because he maintained that his "View" is primarily a vehicle for writing rather than
4560-521: 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
4680-518: Is a cartesian diagram in which the X-axis gauges opinion toward state and centralized government (farthest right being state worship, farthest left being the idea of a state as the "ultimate evil"), and the Y-axis measures the belief that all problems in society have rational solutions (top being complete confidence in rational planning, bottom being complete lack of confidence in rational planning). In
4800-608: 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, 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
4920-553: 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
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5040-510: 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
5160-591: 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
5280-561: 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
5400-414: 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
5520-564: 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
5640-552: The Childe Cycle mercenary stories by Gordon R. Dickson , as well as Heinlein's Starship Troopers , although Pournelle's work takes far fewer technological leaps than either of these. Pournelle was one of the few close friends of H. Beam Piper and was granted by Piper the rights to produce stories set in Piper's Terro-Human Future History. This right has been recognized by the Piper estate. Pournelle worked for some years on
5760-729: 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
5880-586: 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
6000-830: The De La Salle Christian Brothers ; despite its name, it was a high school at the time. He served in the United States Army during the Korean War . In 1953–54, after his military service, Pournelle attended the University of Iowa in Iowa City. Subsequently, he studied at the University of Washington , where he received a B.S. in psychology on June 11, 1955; an M.S. in psychology (experimental statistics) on March 21, 1958; and
6120-627: 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 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
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#17327934219856240-406: 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
6360-430: 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
6480-500: 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
6600-559: 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 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
6720-676: 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
6840-643: The Aerospace Corporation in San Bernardino, California where he was Editor of Project 75 , a major study of all ballistic missile technology for the purpose of making recommendations to the US Air Force on investment in technologies required to build the missile force to be deployed in 1975. After Project 75 was completed Pournelle became manager of several advanced concept studies. At North American Rockwell’s Space Division, Pournelle
6960-513: 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
7080-643: The Catholic Church, he opposed having the government require that Catholic institutions provide access to birth control or abortion. He wrote that Sunday attendance at St. Francis de Sales Catholic Church, in Sherman Oaks, Los Angeles , was part of his family's routine. Upon his death, his family arranged a memorial mass at the church, on 16 September 2017. Pournelle was an intellectual protégé of Russell Kirk and Stefan T. Possony . Pournelle wrote numerous publications with Possony, including The Strategy of Technology (1970). The Strategy has been used as
7200-563: The Human Factors Laboratory at Boeing, where his group did pioneering work on astronaut heat tolerance in extreme environments. His group also did experimental work that resulted in certification of the passenger oxygen system for the Boeing 707 airplane. He later worked as a Systems Analyst in a design and analysis group at the company, where he did strategic analysis of proposed new weapons systems. In 1964, Pournelle joined
7320-412: 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
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#17327934219857440-603: The United States. According to a Wall Street Journal article, "Pournelle estimates that for what the Iraq war has cost so far, the United States could have paid for a network of nuclear power stations sufficient to achieve energy independence, and bankrupt the Arabs for once and for all." Pournelle created the Pournelle chart in his doctoral dissertation, a 2-dimensional coordinate system used to distinguish political ideologies. It
7560-461: 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
7680-584: 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
7800-469: 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
7920-424: 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
8040-522: The Z80 family is the eZ80 , which was offered alongside successor chips. Zilog announced the discontinuation of 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
8160-455: 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
8280-470: 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
8400-580: The Z88 through his Cambridge Computer mail-order company, as he was no longer permitted to use the Sinclair name after the sale. The machine was launched at the Which Computer? Show on 17 February 1987. Early models were contract-manufactured by Thorn EMI but production later switched to SCI Systems in Irvine, Scotland. The Z88 is a notebook computer weighing 0.9 kg (2.0 lb), based on
8520-472: The accompanying letter column became "Chaos Manor Mail". Pournelle still used "Zeke" to write as late as 1987, but admitted that he would soon have to use PCs because tools like Borland Sidekick were unavailable. He hesitated, Pournelle said, because Niven would buy two exact copies of his writing computer and software. He announced in February 1989 that the Smithsonian had asked for "Zeke" as part of
8640-464: 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
8760-614: The approximate accuracy of the term paleoconservatism as applying to him. He distinguished his conservativism from the alternative neoconservatism , noting that he had been drummed out of the Conservative movement by "the egregious Frum", referring to prominent neoconservative, David Frum . Notably, Pournelle opposed the Gulf War and the Iraq War , maintaining that the money would be better spent developing energy technologies for
8880-434: The article: The other day we were sitting around the Byte offices listening to software and hardware explosions going off around us in the microcomputer world. We wondered, "Who could cover some of the latest developments for us in a funny, frank (and sometimes irascible) style?" The phone rang. It was Jerry Pournelle with an idea for a funny, frank (and sometimes irascible) series of articles to be presented in Byte on
9000-509: The batteries. The machine uses a membrane keyboard , which is almost silent in use; an optional electronic "click" can be turned on to indicate keystrokes. The Z88 is powered by four AA batteries , giving up to 20 hours of use. It has three memory card slots, which accommodate proprietary RAM, EPROM or flash cards , the third slot being equipped with a built-in EPROM programmer. Card capacities range from 32 kB to 1 MB . The Z88 has
9120-512: The book Road to Survival by the ecologist (and ornithologist) William Vogt , who depicted an Earth denuded of species other than humans, all of them headed for squalor. Concerned about the Malthusian dangers of human overpopulation , and considering the Catholic Church's position on contraception to be untenable, he left the Catholic Church while an undergraduate at the University of Iowa. Pournelle eventually returned to religion, and for
9240-456: 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
9360-399: The column to his own web site, Chaos Manor Reviews. Pournelle claimed to be the first author to have written a published book contribution using a word processor on a personal computer , in 1977. In the 1980s, Pournelle was an editor and columnist for Survive , a survivalist magazine. He wrote the monthly column "The Micro Revolution" for Popular Computing from April 1984 until
9480-466: The company, he envisioned a weapon consisting of massive tungsten rods dropped from high above the Earth. These super-dense, super-fast kinetic energy projectiles delivered enormous destructive force to the target without contaminating the environs with radioactive isotopes, as would occur with a nuclear bomb. Pournelle named his superweapon “Project Thor”. Others called it " Rods from God ". Pournelle headed
9600-443: The computer's slot. The first generation of card only worked in slot 3 where a 12 V signal (Vpp) is available. The later generation is based on AMD chips and runs with 5 V for erasure. It is possible to read, write and erase flash cards in the three slots and the internal one. It is also possible for an experienced user to replace the built-in 32 kB RAM chip with a bigger 128 or 512 kB static RAM chip. However,
9720-423: The couple had five children. His wife, and son, naval officer Phillip, and daughter, archaeologist Jennifer, have also written science fiction in collaboration with their father. In 2008, Pournelle battled a brain tumor, which appeared to respond favorably to radiation treatment. An August 28, 2008 report on his weblog claimed he was now cancer-free. Pournelle suffered a stroke on December 16, 2014, for which he
9840-502: 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
9960-415: 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
10080-482: 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
10200-571: 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,
10320-622: The earliest versions of what would become the Strategic Defense Initiative . Pournelle was born in Shreveport, Louisiana , the seat of Caddo Parish in northwestern Louisiana , and later lived with his family in Capleville, Tennessee , an unincorporated area near Memphis . Percival Pournelle, his father, was a radio advertising executive and general manager of several radio stations. Ruth Pournelle, his mother,
10440-503: The editor of Astounding Science Fiction (later called Analog Science Fiction and Fact ), but Campbell did not accept any of Pournelle's submissions until shortly before Campbell's death in 1971, when he accepted for publication Pournelle's novelette "Peace with Honor." From the beginning, Pournelle's work has engaged strong military themes. Several books are centered on a fictional mercenary infantry force known as Falkenberg's Legion . There are strong parallels between these stories and
10560-451: The film was in development, and that husband-and-wife writing team, Judith and Garfield Reeves-Stevens , had written the screenplay. Pournelle began fiction writing non-SF work under a pseudonym in 1965. His early SF was published under the name "Wade Curtis", in Analog and other magazines. Some works were also published under the name "J.E. Pournelle". In the mid-1970s, Pournelle began
10680-468: The first bloggers . In the 1960s and early 1970s, he worked in the aerospace industry, but eventually focused on his writing career. In an obituary in Gizmodo , he was described as "a tireless ambassador for the future." Pournelle's hard science fiction writing received multiple awards. In addition to his solo writing, he wrote several novels with collaborators including Larry Niven . Pournelle served
10800-488: The first blogs, entitled "Chaos Manor", which included commentary about politics, computer technology, space technology, and science fiction. Pournelle held paleoconservative political views, which were sometimes expressed in his fiction. He was one of the founders of the Citizens' Advisory Council on National Space Policy , which developed some of the Reagan Administration 's space initiatives, including
10920-486: 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
11040-513: 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
11160-513: The formerly independent sections under 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
11280-631: 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
11400-467: The latter requires some extra board modifications, and 512 kB is the biggest size that can be addressed by the Z88 for the internal RAM. A similar modification is possible for the internal ROM slot. A 512 kB flash chip can replace the original ROM, allowing an upgrade of the operating system. Jerry Pournelle in February 1989 described the Z88 as "the most portable computer I've ever seen", much more so that his Zenith SupersPort 286. He said that
11520-434: The magazine's closure in December 1985. The column focused on the ways microcomputers were reshaping society. In 2011, Pournelle joined journalist Gina Smith , pundit John C. Dvorak , political cartoonist Ted Rall , and several other Byte.com staff reporters to launch an independent tech and political news site, aNewDomain.net Pournelle served as director of aNewDomain until his death. After 1998, Pournelle maintained
11640-427: The next 512 kB are reserved for internal RAM. The next 3 MB are assigned to each one of the three memory slots. Since 1998, a 1 MiB Flash memory card is available which provides convenient non-volatile storage. Once written to the card, files are safe and not reliant on a power supply. Unlike traditional EPROM cards (erased with an external ultraviolet light), this one can be electrically erased in
11760-426: 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
11880-407: 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,
12000-483: 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
12120-418: 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
12240-533: The policy, we certainly did not write the speech… We were not trying to boost space, we were trying to win the Cold War". The Council's first report in 1980 became the transition team policy paper on space for the incoming Reagan administration. The third report was quoted in the Reagan "Star Wars" speech. James Wheatfield wrote that "Pournelle delights in setting up complex background situations and plots, leading
12360-473: The reader step by step towards a solution which is the very opposite of politically correct and… defying a dissenting reader to find where in this logical chain he or she would have acted differently." Pournelle suggested several "laws". He used the term "Pournelle's law" for the expression "One user, one CPU". He later amended this to "One user, at least one CPU" in a column in InfoWorld . He also used
12480-535: 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
12600-517: 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),
12720-467: The screen was small but readable, and thought that his $ 894 estimate for a minimum configuration was "not a lot of money for good hardware". Pournelle said that Pipedream was "disappointingly hard to use", reported that all of his notes in the software from COMDEX had vanished because he did not explicitly save them to memory card, and suggested that the Z88 was best suited as a second computer for students and reporters. Zilog Z80 The Zilog Z80
12840-438: 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
12960-489: The term "Pournelle's law" for "Silicon is cheaper than iron." That is, a computer is cheaper to upgrade than replace. A second aspect of this law was Pournelle's prediction that hard disk drives would eventually be replaced by solid-state memory , although he admitted that bubble memory had failed to do so as he had expected. He has also used "Pournelle's law" to apply to the importance of checking cable connections when diagnosing computer problems: "You'll find by and large,
13080-548: The top rankings in the New York Times Best Seller List . In 1977, Lucifer's Hammer reached number two. Footfall — wherein Heinlein was a thinly veiled minor character — reached the number one spot in 1986. Pournelle served as President of the Science Fiction and Fantasy Writers of America in 1973. In 1994, Pournelle's friendly relationship with Newt Gingrich led to Gingrich securing
13200-409: 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
13320-478: The work on the Intel 4004 , the Intel 8080 and several other ICs. Masatoshi Shima 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
13440-407: 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
13560-560: Was a teacher, although during World War II, she worked in a munitions factory. He attended first grade at St. Anne's Elementary School, in Memphis, which had two grades to a classroom. Beginning with third grade, he attended Coleville Consolidated Elementary School, in Colevile, which had about 25 pupils per grade and four rooms and four teachers for 8 grades Pournelle attended high school at Christian Brothers College in Memphis, run by
13680-605: Was associate director of operations research, where he took part in the Apollo program and general operations. He was founding President of the Pepperdine Research Institute. In 1989, Pournelle, Max Hunter , and retired Army Lieutenant General Daniel O. Graham made a presentation to then Vice President Dan Quayle promoting development of the DC-X rocket. Pournelle was among those who in 1968 signed
13800-454: 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
13920-460: 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
14040-479: Was hospitalized for a time. By June 2015, he was writing again, though impairment from the stroke had slowed his typing. Pournelle died in his sleep of heart failure at his home in Studio City , California, on September 8, 2017. Pournelle was raised a Unitarian . He converted to Roman Catholicism while attending Christian Brothers College. Pournelle was introduced to Malthusian principles upon reading
14160-738: Was later named Executive Assistant to the Mayor in charge of research in September 1969, but resigned from the position after two weeks. After leaving Yorty's office, in 1970 he was a consultant to the Professional Educators of Los Angeles (PELA), a group opposed to the unionization of school teachers in LA. He is sometimes quoted as describing his politics as "somewhere to the right of Genghis Khan." Pournelle resisted others classifying him into any particular political group, but acknowledged
14280-546: 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
14400-531: 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
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