Home computers were a class of microcomputers that entered the market in 1977 and became common during the 1980s. They were marketed to consumers as affordable and accessible computers that, for the first time, were intended for the use of a single, non-technical user. These computers were a distinct market segment that typically cost much less than business, scientific, or engineering-oriented computers of the time, such as those running CP/M or the IBM PC , and were generally less powerful in terms of memory and expandability. However, a home computer often had better graphics and sound than contemporary business computers. Their most common uses were word processing , playing video games , and programming .
137-703: The IBM PCjr (pronounced "PC junior") was a home computer produced and marketed by IBM from March 1984 to May 1985, intended as a lower-cost variant of the IBM PC with hardware capabilities better suited for video games, in order to compete more directly with other home computers such as the Apple II and Commodore 64 . It retained the IBM PC's 8088 CPU and BIOS interface, but provided enhanced graphics and sound, ROM cartridge slots, built-in joystick ports, and an infrared wireless keyboard. The PCjr supported expansion via "sidecar" modules, which could be attached to
274-493: A disk drive (the Commodore 1541 was the only fully-compatible model) or Datasette before they could make use of it as anything but a game machine or TV Typewriter . In the early part of the 1980s, the dominant microprocessors used in home computers were the 8-bit MOS Technology 6502 (Apple, Commodore, Atari, BBC Micro ) and Zilog Z80 ( TRS-80 , ZX81 , ZX Spectrum , Commodore 128 , Amstrad CPC ). One exception
411-614: A shift register . It is similar to the programmable sound generator chips used in game consoles such as the Master System . The PCjr design also allows for an analog sound source in an expansion-bus "sidecar" module, and a software-controlled internal analog switch can select the source for the sound output from among the PC speaker , the SN76489, the cassette port, or the expansion-bus sound source. Only one sound source can be selected at
548-427: A 6502 processor and ran DOS from internal ROM. While this gave Commodore systems some advanced capabilities – a utility program could sideload a disk copy routine onto the drive and return control to the user while the drive copied the disk on its own – it also made Commodore drives more expensive and difficult to clone. Many home computers had a cartridge interface which accepted ROM-based software. This
685-632: A TV or composite monitor. A Motorola 6845 CRTC like the one used in the MDA and CGA adapters, and a custom IBM chip called the Video Gate Array (VGA) constitute the bulk of the PCjr video hardware. Several discrete standard logic devices complete the video subsystem. The 6845 is responsible for the basic raster timing and video data address sequencing, and the Video Gate Array contains all
822-538: A built-in keyboard to support its C7420 Home Computer Module. Among third-generation consoles , Nintendo 's Family Computer offered Family BASIC (sold only in Japan), which included a keyboard that could be connected to an external tape recorder to load and store programs. Books of type-in program listings like BASIC Computer Games were available, dedicated for the BASICs of most models of computer, with titles along
959-604: A common category of utility software in this pre- DMCA era. In another defining characteristic of the home computer, instead of a command line , the BASIC interpreter served double duty as a user interface. Coupled to a character-based screen or line editor , BASIC's file management commands could be entered in direct mode . In contrast to modern computers, home computers most often had their operating system (OS) stored in ROM chips. This made startup times very fast (no more than
1096-576: A dedicated phone line operated bulletin boards of their own. This capability anticipated the internet by nearly 20 years. Some game consoles offered "programming packs" consisting of a version of BASIC in a ROM cartridge . Atari's BASIC Programming for the Atari 2600 was one of these. For the ColecoVision console, Coleco even announced an expansion module which would convert it into a full-fledged computer system. The Magnavox Odyssey² console had
1233-637: A few seconds), but made OS upgrades difficult or impossible without buying a new unit. Usually, only the most severe bugs were fixed by issuing new ROMs to replace the old ones at the user's cost. In addition, the small size and limited scope of home computer "operating systems" (really little more than what today would be called a kernel) left little room for bugs to hide. Although modern operating systems include extensive programming libraries to ease development and promote standardization, home computer operating systems provided little support to application programs. Professionally-written software often switched out
1370-470: A first for a stand-alone computer, costing far less than dedicated motion-video processing equipment costing many thousands of dollars. Stereo sound became standard for the first time; the Atari ST gained popularity as an affordable alternative for MIDI equipment for the production of music. Clock rates on the 68000-based systems were approximately 8 MHz with RAM capacities of 256 kB (for
1507-639: A floppy disk drive. It was available for the TRS-80 and some others. A closely-related technology was the ZX Microdrive , developed by Sinclair Research in the UK, for their ZX Spectrum and QL home computers. Eventually, mass production of 5.25" drives resulted in lower prices, and after about 1984, they pushed cassette drives out of the US home computer market. 5.25" floppy disk drives would remain standard until
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#17327809207151644-432: A game now and then, learn more about computers, and help educate their children". By 1986, industry experts predicted an "MS-DOS Christmas", and the magazine stated that clones threatened Commodore, Atari, and Apple's domination of the home-computer market. The declining cost of IBM compatibles on the one hand, and the greatly-increased graphics, sound, and storage abilities of fourth generation video game consoles such as
1781-732: A great deal of software support from the traditional Japanese publishers of game software. Microsoft developed the MSX-DOS operating system, a version of their popular MS-DOS adapted to the architecture of these machines, that was also able to run CP/M software directly After the first wave of game consoles and computers landed in American homes, the United States Federal Communications Commission (FCC) began receiving complaints of electromagnetic interference to television reception. By 1979
1918-473: A high performer, the Equity was a reliable and compatible design for half the price of a similarly-configured IBM PC. Epson often promoted sales by bundling one of their printers with it at cost. The Equity I sold well enough to warrant the furtherance of the Equity line with the follow-on Equity II and Equity III. In 1986, UK home computer maker Amstrad began producing their PC1512 PC-compatible for sale in
2055-415: A home television. Indeed, the use of a television set as a display almost defines the pre-PC home computer. Although dedicated composite or " green screen " computer displays were available for this market segment and offered a sharper display, a monitor was often a later purchase made only after users had bought a floppy disk drive, printer, modem, and the other pieces of a full system. The reason for this
2192-668: A host of other manufacturers. For many of these businesses, the development of the microcomputer made computing and business software affordable where they had not been before. Introduced in August 1981, the IBM Personal Computer would eventually supplant CP/M as the standard platform used in business. This was largely due to the IBM name and the system's 16 bit open architecture , which expanded maximum memory tenfold, and also encouraged production of third-party clones . In
2329-419: A keyboard integrated into the same case as the motherboard , or, more frequently, a mainboard . While the expandable home computers appeared from the very start (the Apple II offered as many as seven expansion slots) as the whole segment was generally aimed downmarket , few offers were priced or positioned high enough to allow for such expandability. Some systems have only one expansion port, often realized in
2466-407: A light pen (a rarely purchased option), this port can be used in combination with the serial port to supply voltage to a Mouse Systems optical mouse of the same design as those for Sun workstations . The back of the machine does not have any expansion slots. Instead, several permanently mounted, proprietary connectors provide attachment to many built-in hardware capabilities, which replaced many of
2603-686: A palette of 512. MSX was a standard for a home computing architecture that was intended and hoped to become a universal platform for home computing. It was conceived, engineered and marketed by Microsoft Japan with ASCII Corporation . Computers conforming to the MSX standard were produced by most all major Japanese electronics manufacturers, as well as two Korean ones and several others in Europe and South America. Some 5 million units are known to have been sold in Japan alone. They sold in smaller numbers throughout
2740-447: A partially updated version of the data being created by a " writer ". It is very commonly used for computer display images. It is also used to avoid the need to use dual-ported RAM (DPRAM) when the readers and writers are different devices. The Petri net in the illustration shows double buffering. Transitions W1 and W2 represent writing to buffer 1 and 2 respectively while R1 and R2 represent reading from buffer 1 and 2 respectively. At
2877-467: A pixel. Since the PCjr uses the main system RAM for the video buffer, less memory is available for software than on a standard PC, which has separate dedicated video memory in the A000h-BFFFh segments, above conventional memory. The PCjr's sound is provided by a Texas Instruments SN76496 which can produce three square waves of varying amplitude and frequency along with a noise channel powered by
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#17327809207153014-433: A place to plug in cartridge-based games. Usually, the manufacturer would sell peripheral devices designed to be compatible with their computers as extra-cost accessories. Peripherals and software were not often interchangeable between different brands of home computer, or even between successive models of the same brand. To save the cost of a dedicated monitor, the home computer would often connect through an RF modulator to
3151-578: A policy of strictly enforced security. The PCjr's graphics and sound features were superior to the PC's, and PC Magazine speculated that "the PCjr might be the best game machine ever designed". Prominent among launch titles was Sierra's graphical adventure King's Quest I , much of whose $ 850,000 budget was paid by IBM. The PCjr was released in March 1984, missing the 1983 Christmas sales season due to production delays. Even prior to release, anticipation of
3288-491: A program that allowed businesses to sell computers tax-free to its employees, often accompanied by home training programs. Naturally, these businesses chose to equip their employees with the same systems they themselves were using. Today, a computer bought for home use anywhere will be very similar to those used in offices; made by the same manufacturers, with compatible peripherals, operating systems, and application software. Many home computers were superficially similar. Most had
3425-506: A reboot to use the system for something else. In an enduring reflection of their early cassette-oriented nature, most home computers loaded their disk operating system (DOS) separately from the main OS. The DOS was only used for disk and file-related commands and was not required to perform other computing functions. One exception was Commodore DOS , which was not loaded into the computer's main memory at all – Commodore disk drives contained
3562-563: A standard of its own, known as Tandy Graphics Adapter or TGA. Later, Tandy produced Tandy 1000 variants in form factors and price-points even more suited to the home computer market, comprised particularly by the Tandy 1000 EX and HX models (later supplanted by the 1000 RL ), which came in cases resembling the original Apple IIs (CPU, keyboard, expansion slots, and power supply in a slimline cabinet) but also included floppy disk drives. The proprietary Deskmate productivity suite came bundled with
3699-410: A straightforward way. Cartridges can also replace the system BIOS and other firmware. A number of patches from various vendors are included on a single "combo-cartridge", licensed and sold by PC Enterprises, to support add-on hardware, bypass certain limitations of design, and keep up with changing OS requirements. Like the IBM PC, the PCjr uses an Intel 8088 clocked at 4.77 MHz. Despite using
3836-418: A technique for drawing graphics that shows less stutter, tearing , and other artifacts. It is difficult for a program to draw a display so that pixels do not change more than once. For instance, when updating a page of text, it is much easier to clear the entire page and then draw the letters than to somehow erase only the pixels that are used in old letters but not in new ones. However, this intermediate image
3973-413: A time; the sources cannot be mixed. The original keyboard included with the PCjr was a wireless design using infrared line-of-sight communication, which IBM initially marketed as the "Freeboard." This is a chiclet keyboard with small, flat, calculator style plastic keycaps. The keycaps are blank, with the labels printed between keys so that overlays can be used. The PCjr keyboard has 62 keys rather than
4110-485: A turbo NEC V40 CPU (up-rated 8088) which was rather slow for its time, but the video monitor did feature 400-pixel vertical resolution. This unique computer failed for the same reasons as did IBM's PCjr: poor performance and expandability, and a price too high for the home market. Another company that offered low-cost PCs for home use was Leading Edge , with their Model M and Model D computers. These were configured like full-featured business PCs, yet still could compete in
4247-448: A video mode switch. Of the three new modes, 160 x 200 x 16 mode has the same layout as CGA graphics modes; the odd and even scanlines are stored in the first and second half of the video buffer, each half being 8k in size, and every four bits represents one pixel. The 320 x 200 x 16 and 640 x 200 x 4 modes have four blocks of scanlines; every four or two bits respectively represents
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4384-486: Is a swap chain three buffers long. After the program has drawn both back buffers, it waits until the first one is placed on the screen, before drawing another back buffer (i.e. it is a 3-long first in, first out queue). Most Windows games seem to refer to this method when enabling triple buffering. The term quad buffering is the use of double buffering for each of the left and right eye images in stereoscopic implementations, thus four buffers total (if triple buffering
4521-425: Is a different "back buffer" for every window containing the non-composited image of the entire window contents. In the page-flip method, instead of copying the data, both buffers are capable of being displayed. At any one time, one buffer is actively being displayed by the monitor, while the other, background buffer is being drawn. When the background buffer is complete, the roles of the two are switched. The page-flip
4658-498: Is being drawn. The currently active and visible buffer is called the front buffer , while the background page is called the back buffer . In computer graphics , triple buffering is similar to double buffering but can provide improved performance. In double buffering, the program must wait until the finished drawing is copied or swapped before starting the next drawing. This waiting period could be several milliseconds during which neither buffer can be touched. In triple buffering,
4795-460: Is enough memory, a feature missing from the CGA. The CGA also did not provide a VBLANK interrupt, making it hard to detect when the screen was beginning to be drawn, but the PCjr provides this on IRQ 5, an important feature for smooth page-flipping. The video system also has a "blink" feature which toggles the palette between the first and second groups of eight palette registers at the same rate used for
4932-405: Is often called a "back buffer". When all drawing operations are considered complete, the whole region (or only the changed portion) is copied into the video RAM (the "front buffer"); this copying is usually synchronized with the monitor's raster beam in order to avoid tearing. Software implementations of double buffering necessarily require more memory and CPU time than single buffering because of
5069-450: Is seen by the user as flickering . In addition, computer monitors constantly redraw the visible video page (traditionally at around 60 times a second), so even a perfect update may be visible momentarily as a horizontal divider between the "new" image and the un-redrawn "old" image, known as tearing . A software implementation of double buffering has all drawing operations store their results in some region of system RAM ; any such region
5206-401: Is typically accomplished by modifying a hardware register in the video display controller —the value of a pointer to the beginning of the display data in the video memory. The page-flip is much faster than copying the data and can guarantee that tearing will not be seen as long as the pages are switched over during the monitor's vertical blanking interval —the blank period when no video data
5343-547: Is used for copying data between two buffers for direct memory access (DMA) transfers, not for enhancing performance, but to meet specific addressing requirements of a device (esp. 32-bit devices on systems with wider addressing provided via Physical Address Extension ). DOS and Windows device drivers are a place where the term "double buffering" is likely to be used. Linux and BSD source code calls these "bounce buffers". Some programmers try to avoid this kind of double buffering with zero-copy techniques. Double buffering
5480-458: The Apple IIe . IBM repeatedly denied these rumors, but customers visited stores attempting to buy the product and rivals' revenue, product plans, and share prices reacted to the officially nonexistent computer in what the press called "Peanut Panic" or "The Great Peanut Roast". By September 1983, books and magazine articles on Peanut were ready for publishing, with only a few changes needed once
5617-556: The Atari 1040ST (not the 520ST), Amiga , and Tandy 1000 , did house floppy drive(s) internally. At any rate, to expand any computer with additional floppy drives, external units would have to be plugged in. Toward the end of the home computer era, drives for a number of home computer models appeared offering disk-format compatibility with the IBM PC. The disk drives sold with the Commodore 128, Amiga, and Atari ST were all able to read and write PC disks, which themselves were undergoing
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5754-410: The BASIC programming language included on the system ROM , it was easy for users to get started creating their own simple applications. Many users found programming to be a fun and rewarding experience, and an excellent introduction to the world of digital technology. The line between 'business' and 'home' computer market segments vanished completely once IBM PC compatibles became commonly used in
5891-468: The Commodore PET , and the original Apple II in 1977, almost every manufacturer of consumer electronics rushed to introduce a home computer. Large numbers of new machines of all types began to appear during the late 1970s and early 1980s. Mattel , Coleco , Texas Instruments , and Timex , none of which had any prior connection to the computer industry, all had short-lived home computer lines in
6028-465: The Motorola 68008 with its external 8-bit bus). Graphics resolutions approximately doubled to give roughly NTSC -class resolution, and color palettes increased from dozens to hundreds or thousands of colors available. The Amiga was built with a custom chipset with dedicated graphics and sound coprocessors for high-performance video and audio. The Amiga found use as a workstation for desktop video ,
6165-505: The Nintendo Entertainment System , but no longer sold home computers. Toward the end of the 1980s, clones also became popular with non-corporate customers. Inexpensive, highly-compatible clones succeeded where the PCjr had failed. Replacing the hobbyists who had made up the majority of the home computer market were, as Compute! described them, "people who want to take work home from the office now and then, play
6302-484: The PCjr as a PC/DOS-compatible machine aimed squarely at the home user. It proved a spectacular failure because IBM deliberately limited its capabilities and expansion possibilities in order to avoid cannibalizing sales of the profitable PC. IBM management believed that if they made the PCjr too powerful, too many buyers would prefer it over the bigger, more expensive PC. Poor reviews in the computer press and poor sales doomed
6439-554: The Sega Genesis and Super Nintendo Entertainment System on the other, combined to cause the market segment for home computers to vanish by the early 1990s in the US. In Europe, the home computer remained a distinct presence for a few years more, with the low-end models of the 16-bit Amiga and Atari ST families being the dominant players, but by the mid-1990s, even the European market had dwindled. The Dutch government even ran
6576-424: The 83 of the PC keyboard, and the remaining keys must be entered by holding a modifier key. For infrared wireless operation, the keyboard is powered by four AA cells. Certain types of room lighting can cause interference with the infrared keyboard sensor, and multiple keyboards cannot be used wirelessly in the same room without problems. IBM sold a cable which could be plugged in between the keyboard and computer if
6713-541: The Atari and Commodore 8-bit machines, coprocessors were added to speed processing of graphics and audio data. For these computers, clock rate was considered a technical detail of interest only to users needing accurate timing for their own programs. To economize on component cost, often the same crystal used to produce color television-compatible signals was also divided down and used for the processor clock. This meant processors rarely operated at their full rated speed, and had
6850-534: The BASIC interpreter was also used as the user interface , and given tasks such as loading, saving, managing, and running files. One exception was the Jupiter Ace , which had a Forth interpreter instead of BASIC. A built-in programming language was seen as a requirement for any computer of the era, and was the main feature setting home computers apart from video game consoles . Still, home computers competed in
6987-503: The BIOS routines for handling floppy access were different and more complex than those on the PC. Software that tried to perform direct, low-level disk access (mainly utilities, but also the occasional game such as Dunzhin: Warrior of Ras ) would not work unless it was rewritten for the PCjr. IBM's first home computer was the PC, released in 1981. Within two years the PC had created a large new ecosystem of hardware and software, nearly leading
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#17327809207157124-526: The Color Select Register (at I/O addresses 3D8h and 3D9h respectively), are not compatible, as the PCjr provides the equivalent functionality through different registers inside the Video Gate Array which are accessed in a completely different manner through a single I/O address (3DAh). The 6845 CRTC and the VGA together are responsible for refreshing the internal DRAM of the PCjr, which complicates
7261-471: The FCC demanded that home computer makers submit samples for radio frequency interference testing. It was found that "first generation" home computers emitted too much radio frequency noise for household use. The Atari 400 and 800 were designed with heavy RF shielding to meet the new requirements. Between 1980 and 1982 regulations governing RF emittance from home computers were phased in. Some companies appealed to
7398-417: The FCC to waive the requirements for home computers, while others (with compliant designs) objected to the waiver. Eventually techniques to suppress interference became standardized. Multiple buffering In computer science , multiple buffering is the use of more than one buffer to hold a block of data , so that a " reader " will see a complete (though perhaps old) version of the data instead of
7535-526: The Macintosh itself was too expensive for most households. The Amiga in particular had true multitasking capability, and unlike all other low-cost computers of the era, could run multiple applications in their own windows. The second generation of MSX computers (MSX2) achieved the performance of high-performance computers using a high-speed video processor ( Yamaha V9938 ) capable of handling resolutions of 512 × 424 pixels, and 256 simultaneous colors from
7672-495: The PC Portable, but the PCjr units were specially equipped with a small fan to prevent overheating since the computer did not have a case fan. The front of the PCjr exposes a pair of cartridge slots in which the user can insert software on ROM cartridges, as was common with other home computers. Each cartridge can contain up to 64 KB of ROM. When a ROM cartridge is inserted, the machine can automatically restart and boot off of
7809-454: The PCjr video subsystem continuously refreshes the system internal DRAM transparently, without disturbing the CPU, programs running from ROM on the PCjr may actually run slightly faster on the PCjr than on an IBM PC or XT. Unlike the IBM PC, which required a separate video card, the PCjr display hardware was built in to the system board. At the time, the only cards available from IBM for the PC were
7946-509: The PCjr was PC DOS, like the IBM PC, and it supported a large amount of PC software, with some incompatibilities. PC DOS 2.10 is the minimum version of DOS required for the PCjr. IBM's OEM versions of MS-DOS supported the machine up to DOS 3.30, but memory expansion was required for DOS 3.20 and 3.30. Like the original PC, the PCjr has BASIC in ROM, but includes Cartridge BASIC instead of Cassette BASIC. In addition to cartridge support, it extended
8083-509: The PCjr was not growing as rapidly as expected. By May 1984 it had only sold 10,000 units, while other companies were reported to be slow in developing software for the system. Home computer Home computers were usually sold already manufactured in stylish metal or plastic enclosures. However, some home computers also came as commercial electronic kits , like the Sinclair ZX80 , which were both home and home-built computers since
8220-467: The PCjr. Tandy Corporation capitalized on IBM's blunder with its PCjr-compatible Tandy 1000 in November. Like the PCjr, it was pitched as a home, education, and small-business computer, featuring joystick ports, better sound and graphics (same as the PCjr but with enhancements), combined with near-PC/DOS compatibility (unlike Tandy's earlier Tandy 2000 ). The improved Tandy 1000 video hardware became
8357-532: The PCs blinking text attribute, and a palette bit-masking feature that can be used to switch between palette subsets without reprogramming palette registers. Unlike CGA, PCjr has palette registers which allow the colors in all modes to be chosen from the full 16-color RGBI palette. When the BIOS is used to set a video mode, it sets up the palette table to emulate the CGA color palette for that mode. Programs specifically written to use PCjr graphics can subsequently reprogram
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#17327809207158494-444: The ROM, without requiring the user to manually reboot. This auto-restart function is an optional feature of each cartridge: a cartidge can either restart the machine or not when it is inserted, depending on the construction of the cartridge. PCjr catridges are strictly read-only, unlike the software cartridges of some other contemporary computers and game consoles which can also be equipped with read/write memory (RAM) or I/O hardware in
8631-519: The ROM-based OS anyway to free the address space it occupied and maximize RAM capacity. This gave the program full control of the hardware and allowed the programmer to optimize performance for a specific task. Games would often turn off unused I/O ports, as well as the interrupts that served them. As multitasking was never common on home computers, this practice went largely unnoticed by users. Most software even lacked an exit command, requiring
8768-549: The Tandy 1000s. Deskmate was suited to use by computer novices with its point-and-click (though not graphical) user interface. From the launch of the Tandy 1000 series, their manufacture were price-competitive because of Tandy's use of high-density ASIC chip technology, which allowed their engineers to integrate many hardware features into the motherboard (obviating the need for circuit cards in expansion slots as with other brands of PC). Tandy never transferred its manufacturing operation to Asia; all Tandy desktop computers were built in
8905-664: The UK. Later they would market the machine in the US as the PC6400. In June 1987, an improved model was produced as the PC1640. These machines had fast 8086 CPUs, enhanced CGA graphics, and were feature-laden for their modest prices. They had joystick adapters built into their keyboards and shipped with a licensed version of the Digital Research 's GEM , a GUI for the MS-DOS operating system. They became marginal successes in
9042-654: The USA (this was not true of the laptop and pocket computers, nor peripherals). In 1985, the Epson corporation, a popular and respected producer of inexpensive dot-matrix printers and business computers (the QX-10 and QX-16 ), introduced its low-cost Epson Equity PC. Its designers took minor shortcuts, such as few expansion slots and a lack of a socket for an 8087 math chip, but Epson did bundle some utility programs that offered decent turnkey functionality for novice users. While not
9179-431: The ability to run industry-standard MS-DOS software on affordable, user-friendly PCs was anticipated as a source of new sales. Furthermore, many in the industry felt that MS-DOS would eventually (inevitably, it seemed) come to dominate the computer business entirely, and some manufacturers felt the need to offer individual customers PC-style products suitable for the home market. In early 1984, market colossus IBM produced
9316-530: The additional timing logic, video data demultiplexing logic, color processing logic, and programmable palette table logic, as well as the logic for multiplexing RAM access between the 8088 CPU and the video generation circuitry. For programming, the CRTC is generally compatible with the CGA at the hardware register level. Some other CGA programming details, in particular the Mode Control Register and
9453-481: The author to obtain the programs on disk or cassette for a few dollars. Before the Internet, and before most computer owners had a modem , books were a popular and low-cost means of software distribution—one that had the advantage of incorporating its own documentation. These books also served a role in familiarizing new computer owners with the concepts of programming; some titles added suggested modifications to
9590-477: The base Amiga 1000 ) up to 1024 kB ( 1 MB , a milestone, first seen on the Atari 1040ST). These systems used 3.5" floppy disks from the beginning, but 5.25" drives were made available to facilitate data exchange with IBM PC compatibles. The Amiga and ST both had GUIs with windowing technology. These were inspired by the Macintosh , but at a list price of US$ 2,495 (equivalent to $ 7,100 in 2023),
9727-401: The beginning, only the transition W1 is enabled. After W1 fires, R1 and W2 are both enabled and can proceed in parallel. When they finish, R2 and W1 proceed in parallel and so on. After the initial transient where W1 fires alone, this system is periodic and the transitions are enabled – always in pairs (R1 with W2 and R2 with W1 respectively). In computer graphics , double buffering is
9864-500: The buyer would fill with the integrated circuits , other individual electronic components, wires and connectors, and then hand- solder all the connections. While two early home computers ( Sinclair ZX80 and Acorn Atom ) could be bought either in kit form or assembled, most home computers were only sold pre-assembled. They were enclosed in plastic or metal cases similar in appearance to typewriter or hi-fi equipment enclosures, which were more familiar and attractive to consumers than
10001-413: The computer, stating that it would cost $ 600 plus $ 400 for a disk drive, use a color TV as a display, and have a standard typewriter keyboard. IBM announced the PCjr on November 1, 1983, at its New York City headquarters with an enormous amount of advance publicity, including live news coverage of the event. Experts predicted, according to The Washington Post , that the PCjr would "quickly become
10138-477: The default PC floppy was double-sided, with about twice the storage capacity of floppy disks used by 8-bit home computers. PC drives tended to cost less because they were most often built-in, requiring no external case, controller, or power supply. The faster clock rates and wider buses available to later Intel CPUs compensated somewhat for the custom graphics and sound chips of the Commodores and Ataris. In time,
10275-478: The early 1980s. Some home computers were more successful. The BBC Micro , Sinclair ZX Spectrum , Atari 8-bit computers , and Commodore 64 sold many units over several years and attracted third-party software development. Almost universally, home computers had a BASIC interpreter combined with a line editor in permanent read-only memory , which one could use to type in BASIC programs and execute them immediately, or save them to tape or disk. In direct mode ,
10412-493: The end of the 8-bit era. Though external 3.5" drives were made available for home computer systems toward the latter part of the 1980s, almost all software sold for 8-bit home computers remained on 5.25" disks. 3.5" drives were used for data storage, with the exception of the Japanese MSX standard, on which 5.25" floppies were never popular. Standardization of disk formats was not common; sometimes, even different models from
10549-416: The family TV set, which served as both video display and sound system. The rise of the home computer also led to a fundamental shift during the early 1980s in where and how computers were purchased. Traditionally, microcomputers were obtained by mail order or were purchased in person at general electronics retailers like RadioShack . Silicon Valley , in the vanguard of the personal computer revolution,
10686-423: The features that PC expansion cards provided, including: Internally the PCjr did have expansion slots to support specific upgrades: a RAM upgrade, a modem, and a floppy drive. On the right side of the machine, the system bus was exposed for use with "sidecars," upgrade modules which attached to the side of the machine. Third-party manufacturers produced a number of expansion units for the PCjr. The primary OS for
10823-465: The few business users. Various copy protection schemes were developed for floppy disks; most were broken in short order. Many users would only tolerate copy protection for games, as wear and tear on disks was a significant issue in an entirely floppy-based system. The ability to make a "working backup" disk of vital application software was seen as important. Copy programs that advertised their ability to copy or even remove common protection schemes were
10960-451: The first 64 KB or 128 KB of RAM inside the system unit itself, and not to programs or data located in ROM - including software on ROM cartridges plugged into the front of the PCjr - or in additional RAM in a sidecar attachment. Under these circumstances the PCjr should run at full speed. The most common instances in which this maximum speed would be achieved are when running games or productivity applications from ROM cartridges. In fact, because
11097-477: The form of cumbersome "sidecar" systems, such as on the TI-99/4 , or required finicky and unwieldy ribbon cables to connect the expansion modules. Sometimes they were equipped with a cheap membrane or chiclet keyboard in the early days, although full-travel keyboards quickly became universal due to overwhelming consumer preference. Most systems could use an RF modulator to display 20–40 column text output on
11234-606: The game console showed a blank screen or continued playing the same repetitive game. Another capability home computers had that game consoles of the time lacked was the ability to access remote services over telephone lines by adding a serial port interface, a modem , and communication software . Though it could be costly, it permitted the computer user to access services like Compuserve , and private or corporate bulletin board systems and viewdata services to post or read messages, or to download or upload software. Some enthusiasts with computers equipped with large storage capacity and
11371-440: The graphics card never has to wait for the software to complete. Consequently, the software and the graphics card are completely independent and can run at their own pace. Finally, the displayed image was started without waiting for synchronization and thus with minimum lag. Due to the software algorithm not polling the graphics hardware for monitor refresh events, the algorithm may continuously draw additional frames as fast as
11508-414: The growing popularity of home PCs spurred many software publishers to offer gaming and children's software titles. Many decision-makers in the computer industry believed there could be a viable market for office workers who used PC/DOS computers at their jobs and would appreciate an ability to bring diskettes of data home on weeknights and weekends to continue work after-hours on their "home" computers. So,
11645-462: The hardware can render them. For frames that are completed much faster than interval between refreshes, it is possible to replace a back buffers' frames with newer iterations multiple times before copying. This means frames may be written to the back buffer that are never used at all before being overwritten by successive frames. Nvidia has implemented this method under the name "Fast Sync". An alternative method sometimes referred to as triple buffering
11782-487: The home computer market with 26% of all microcomputers sold in 1983, second only to the much less expensive Commodore 64 . For a year before the PCjr's announcement, the computer industry discussed rumors of a new IBM product, code named "Peanut", that would repeat the PC's success. The rumors described Peanut as a home computer with 64 kB of memory that would be IBM PC compatible , benefit from IBM's service network and, at US$ 600 to US$ 1,000 , be less expensive than
11919-451: The home market on price because Leading Edge had access to low-cost hardware from their Asian manufacturing partners Mitsubishi with the Model M and Daewoo with the Model D. The LEWP was bundled with the Model D. It was favorably reviewed by the computer press and sold very well. By the mid '80s, the market for inexpensive PCs for use in the home market was expanding at such a rate that
12056-483: The home market. In 1987, longtime small computer maker Zenith introduced a low-cost PC they called the EaZy PC . This was positioned as an "appliance" computer much like the original Apple Macintosh: turnkey startup, built-in monochrome video monitor, and lacking expansion slots, requiring proprietary add-ons available only from Zenith, but instead with the traditional MS-DOS Command-line interface . The EaZy PC used
12193-489: The home". In 1990, the company reportedly refused to support joysticks on its low-cost Macintosh LC and IIsi computers to prevent customers from considering them as "game machines". Although the Apple II and Atari computers are functionally similar, Atari's home-oriented marketing resulted in a game-heavy library with much less business software. By the late 1980s, many mass merchants sold video game consoles like
12330-484: The home, since now both categories of computers typically use the same processor architectures, peripherals, operating systems, and applications. Often, the only difference may be the sales outlet through which they are purchased. Another change from the home computer era is that the once-common endeavor of writing one's own software programs has almost vanished from home computer use. As early as 1965, some experimental projects, such as Jim Sutherland's ECHO IV , explored
12467-462: The image of, as Compute! wrote, "a low-powered, low-end machine primarily suited for playing games". Apple consistently avoided stating that it was a home-computer company, and described the IIc as "a serious computer for the serious home user", despite competing against IBM's PCjr home computer. John Sculley denied that his company sold home computers; rather, he said, Apple sold "computers for use in
12604-609: The industrial metal card-cage enclosures used by the Altair and similar computers. The keyboard - a feature lacking on the Altair - was usually built into the same case as the motherboard . Ports for plug-in peripheral devices such as a video display, cassette tape recorders, joysticks , and (later) disk drives were either built-in or available on expansion cards . Although the Apple II had internal expansion slots, most other home computer models' expansion arrangements were through externally-accessible 'expansion ports' that also served as
12741-406: The late 1970s, the 6502-based Apple II had carved out a niche for itself in business, thanks to the industry's first killer app , VisiCalc , released in 1979. However, the Apple II would quickly be displaced for office use by IBM PC compatibles running Lotus 1-2-3 . Apple Computer 's 1980 Apple III was underwhelming, and although the 1984 release of the Macintosh introduced the modern GUI to
12878-402: The lines of 64 Amazing BASIC Games for the Commodore 64 . While most of the programs in these books were short and simple games or demos , some titles, such as Compute! ' s SpeedScript series, contained productivity software that rivaled commercial packages. To avoid the tedious process of typing in a program listing from a book, these books would sometimes include a mail-in offer from
13015-490: The machine was mixed. Ziff Davis , publisher of the successful PC Magazine , printed the first issue of PCjr Magazine before the first units shipped, and competing computer magazines included Peanut , PCjr World , jr , and Compute! for the PC and PCjr . However, as new information became available about the machine, retailers became deeply concerned about its marketability. When the PCjr became widely available in March 1984 sales were below expectations. Consumer interest
13152-400: The market four days before IBM's announcement, after losing US$ 223 million in nine months against Commodore by selling its 99/4A for as low as $ 99 . Developers began creating PCjr software in 1982. Sierra On-Line , SPC , and The Learning Company were among those that produced games, productivity, and educational software as launch titles , using detailed IBM production outlines under
13289-464: The market, it was not common until IBM-compatible computers adopted it. Throughout the 1980s, businesses large and small adopted the PC platform, leading, by the end of the decade, to sub-US$ 1000 IBM PC XT -class white box machines, usually built in Asia and sold by US companies like PCs Limited . In 1980, Wayne Green , the publisher of Kilobaud Microcomputing , recommended that companies avoid
13426-788: The monochrome MDA and color CGA boards. PCjr graphics were similar to CGA, with several new video modes: The primary improvement over CGA is the greater color depth. CGA could only display 4 colors in its medium-resolution mode, and 2 colors in high-resolution. The PCjr increases these to 16 and 4 colors. Video modes on the PCjr use varying amounts of system memory: 40 x 25 text mode uses 1 KB, for instance, while 320 x 200 x 16 and 640 x 200 x 4 use 32 KB. These latter two modes, as well as 80 x 25 text mode, are referred to in documentation as "high bandwidth modes" and are unsupported on base models with only 64 KB of memory. Multiple text or graphics pages can be used for page-flipping as long as there
13563-664: The new machine and its MS-DOS operating system. Even basic PCs cost thousands of dollars and were far out of reach for typical home computer users. However, in the following years, technological advances and improved manufacturing capabilities (mainly greater use of robotics and relocation of production plants to lower-wage locations in Asia) permitted several computer companies to offer lower-cost, PC-style machines that would become competitive with many 8-bit home-market pioneers like Radio Shack, Commodore, Atari, Texas Instruments, and Sinclair. PCs could never become as affordable as these because
13700-431: The palette table to use any colors desired. Palette changes must be made during horizontal or vertical blanking periods of a video frame in order to avoid disrupting the display (transiently during the palette change). The monitor included with the PCjr is a 12" TTL RGBI display like those supported by the CGA, but including an internal amplified speaker. Also like CGA, the PCjr supported composite video out for use with
13837-757: The possible utility of a computer in the home. In 1969, the Honeywell Kitchen Computer was marketed as a luxury gift item, and would have inaugurated the era of home computing, but none were sold. Computers became affordable for the general public in the 1970s due to the mass production of the microprocessor , starting in 1971. Early microcomputers such as the Altair 8800 had front-mounted switches and diagnostic lights (nicknamed " blinkenlights ") to control and indicate internal system status, and were often sold in kit form to hobbyists. These kits would contain an empty printed circuit board which
13974-546: The price difference between old 8-bit technology and new PCs. Despite their higher absolute prices, PCs were perceived by many to be better values for their utility as superior productivity tools and their access to industry-standard software. Another advantage was the 8088/8086's wide, 20-bit address bus. The PC could access more than 64 kilobytes of memory relatively inexpensively (8-bit CPUs, which generally had multiplexed 16-bit address buses, required complicated, tricky memory management techniques like bank-switching ). Similarly,
14111-403: The process of switching video modes on the PCjr. Resetting the VGA, which must be done during certain video mode switches, must be done by code not running from the system RAM controlled by the VGA, and if the CRTC or the VGA is disabled for too long, the contents of the internal RAM can be lost. Additional external DRAM (in sidecar expansion modules) is refreshed independently and never affected by
14248-418: The program has two back buffers and can immediately start drawing in the one that is not involved in such copying. The third buffer, the front buffer, is read by the graphics card to display the image on the monitor. Once the image has been sent to the monitor, the front buffer is flipped with (or copied from) the back buffer holding the most recent complete image. Since one of the back buffers is always complete,
14385-474: The program listings for the user to carry out. Applying a patch to modify software to be compatible with one's system, or writing a utility program to fit one's needs, was a skill every advanced computer owner was expected to have. During the peak years of the home computer market, scores of models were produced, usually as individual design projects with little or no thought given to compatibility between different manufacturers, or even within product lines of
14522-561: The purchaser could assemble the unit from a kit. Advertisements in the popular press for early home computers were rife with possibilities for their practical use in the home, from cataloging recipes to personal finance to home automation , but these were seldom realized in practice. For example, using a typical 1980s home computer as a home automation appliance would require the computer to be kept powered on at all times and dedicated to this task. Personal finance and database use required tedious data entry . By contrast, advertisements in
14659-501: The recording back through the modem to "load". Most cassette implementations were notoriously slow and unreliable, but 8" drives were too bulky for home use, and early 5.25" form-factor drives were priced for business use, out of reach of most home buyers. An innovative alternative was the Exatron Stringy Floppy , a continuous-loop tape drive which was much faster than a data cassette drive and could perform much like
14796-444: The same CPU and clock speed, performance is often inferior to the PC, because access to system RAM is delayed by wait states added by the Video Gate Array to synchronize shared access to RAM between the CPU and the video hardware. IBM claimed that an average of two wait states are added, but the designers of the Tandy 1000, a clone of the PCjr, claimed that six was a more accurate figure. This delay only applies to software resident in
14933-518: The same manufacturer used different disk formats. Almost universally, the floppy disk drives available for 8-bit home computers were housed in external cases, with their own controller boards and power supplies contained within. Only the later, advanced 8-bit home computers housed their drives within the main unit; these included the TRS-80 Model III , TRS-80 Model 4 , Apple IIc , MSX2 , and Commodore 128D . The later 16-bit machines, such as
15070-445: The same manufacturer. Except for the Japanese MSX standard, the concept of a computer platform was still forming, with most companies considering rudimentary BASIC language and disk format compatibility sufficient to claim a model as "compatible". Things were different in the business world, where cost-conscious small business owners had been using CP/M running on Z80 -based computers from Osborne , Kaypro , Morrow Designs , and
15207-473: The same market as the consoles. A home computer was often seen as simply a higher-end purchase than a console, adding abilities and productivity potential to what would still be mainly a gaming device. A common marketing tactic was to show a computer system and console playing games side by side, then emphasizing the computer's greater ability by showing it running user-created programs, education software, word processing, spreadsheet, and other applications, while
15344-418: The same price-reducing measures were available to all computer makers. Furthermore, software and peripherals for PC-style computers tended to cost more than those for 8-bit computers because of the anchoring effect caused by the pricey IBM PC. As well, PCs were inherently more expensive since they could not use the home TV set as a video display. Nonetheless, the overall reduction in manufacturing costs narrowed
15481-437: The side of the unit. Despite widespread anticipation, the PCjr was ultimately unsuccessful in the market. It was only partially IBM PC compatible , limiting support for IBM's software library, its chiclet keyboard was widely criticized for its poor quality and limited expandability, and it was initially offered with a maximum of 128 KB of RAM, insufficient for many PC programs. The PCjr came in two models: The PCjr
15618-444: The side-effect that European and North American versions of the same home computer operated at slightly different speeds and different video resolution due to different television standards. Initially, many home computers used the then-ubiquitous compact audio cassette as a storage mechanism. A rough analogy to how this worked would be to place a recorder on the phone line as a file was uploaded by modem to "save" it, and playing
15755-405: The specialty computer press often simply listed specifications, assuming a knowledgeable user who already had applications in mind. If no packaged software was available for a particular application, the home computer user could program one—provided they had invested the requisite hours to learn computer programming , as well as the idiosyncrasies of their system. Since most systems arrived with
15892-457: The standard IBM BASIC with commands to support the new video and audio functionality. The system will boot into Cartridge BASIC if no cartridge or boot disk is present. The register mapping of the PCjr's video hardware is different from the IBM CGA card, so software that tries to modify or read registers directly will not work. The PCjr has a "gate" register to which software writes the number of
16029-414: The standard by which all other home computers are measured" and estimated sales of one million or more in 1984, expecting the PCjr to change the home-computer market in a similar way to how the IBM PC had changed the business-microcomputer market. They predicted that the PCjr would extend IBM's dominance, with customers able to use the company's computers in the home and in the office. Texas Instruments left
16166-419: The still officially nonexistent computer appeared. Software companies prepared to market products as "Peanut compatible" with the computer of which, rumors said, IBM would produce 500,000 units in the first year. Adweek estimated that IBM would spend $ 75 million on marketing, including an alleged license of Charles Schulz 's Peanuts characters. Smalltalk magazine in August published a detailed article on
16303-411: The system memory allocated for the back buffer, the time for the copy operation, and the time waiting for synchronization. Compositing window managers often combine the "copying" operation with " compositing " used to position windows, transform them with scale or warping effects, and make portions transparent. Thus, the "front buffer" may contain only the composite image seen on the screen, while there
16440-406: The term "home computer" in their advertising, as it "I feel is self-limiting for sales...I prefer the term "microcomputers" since it doesn't limit the uses of the equipment in the imagination of the prospective customers". With the exception of Tandy, most computer companies – even those with a majority of sales to home users – agreed, avoiding the term "home computer" because of its association with
16577-599: The time 1801 series CPU , offering a full PDP-11 compatibility and a fully functional Q-Bus slot, though at the cost of very anemic RAM and graphics. The Motorola 6809 was used by the Radio Shack TRS-80 Color Computer , the Fujitsu FM-7 , and Dragon 32/64 . Processor clock rates were typically 1–2 MHz for 6502 and 6809-based CPUs and 2–4 MHz for Z80-based systems (yielding roughly equal performance), but this aspect
16714-501: The transition from 5.25" to 3.5" format at the time (though 5.25" drives remained common on PCs until the late 1990s, due to existence of the large software and data archives on five-inch floppies). 5.25" drives were made available for the ST, Amiga, and Macintosh, otherwise 3.5" based systems with no other use for a 5.25" format. Hard drives were never popular on home computers, remaining an expensive, niche product mainly for BBS sysops and
16851-836: The two leaders in the US, Commodore and Atari, themselves felt compelled to enter the market with their own lines. They were only marginally successful compared to other companies that made only PCs. Still, later prices of white box PC clone computers by various manufacturers became competitive with the higher-end home computers (see below). Throughout the 1980s, costs and prices continued to be driven down by: advanced circuit design and manufacturing, multi-function expansion cards, shareware applications such as PC-Talk , PC-Write , and PC-File , greater hardware reliability, and more user-friendly software that demanded less customer support services. The increasing availability of faster processor and memory chips, inexpensive EGA and VGA video cards, sound cards , and joystick adapters also bolstered
16988-403: The user wanted a more reliable connection, which also eliminated the need for batteries, since the keyboard IR receiver is automatically disabled when the cord is attached to the computer. The chiclet design was not well received, and in 1984 IBM began shipping a new design, still wireless, but using more conventionally shaped keycaps. The PCjr also has a light pen port. Besides being used for
17125-509: The viability of PC/DOS computers as alternatives to specially-made computers and game consoles for the home. From about 1985, the high end of the home computer market began to be dominated by "next-generation" home computers using the 16-bit Motorola 68000 chip, which enabled the greatly-increased abilities of the Amiga and Atari ST series (in the UK, the Sinclair QL was built around
17262-405: The video area from address 0xB8000 through 0xBFFFF. The PCjr's video memory cannot be moved above 128k if expansion memory is added, so some PC software that ran off of self-booting disks would not work on a PCjr if the software required more than 128k of RAM. The floppy controller on the PCjr also had its I/O registers mapped into different ports than on the PC, and since the PCjr did not have DMA,
17399-424: The video register to be accessed, followed by the value to be written into it. Alteration of other CRTC registers cannot be assumed to produce the same results from the PCjr video system as from the CGA. Programs for the CGA that manipulate the CRTC start address, and that rely on address wrap-around above address 0xBC000, may not work correctly on the PCjr because it always has a 32 KB contiguous block of RAM in
17536-548: The world. Due to the "price wars" being waged in the USA home computer market during the 1983-85 period, MSX computers were never marketed to any great extent in the USA. Eventually more advanced mainstream home computers and game consoles obsoleted the MSX machines. The MSX computers were built around the Zilog Z80 8-bit processor, assisted with dedicated video graphics and audio coprocessors supplied by Intel , Texas Instruments , and General Instrument . MSX computers received
17673-573: Was also used for expansion or upgrades such as fast loaders . Application software on cartridge did exist, which loaded instantly and eliminated the need for disk swapping on single-drive setups, but the vast majority of cartridges were games. From the introduction of the IBM Personal Computer (ubiquitously known as the PC) in 1981, the market for computers meant for the corporate, business, and government sectors came to be dominated by
17810-527: Was manufactured for IBM in Lewisburg, Tennessee by Teledyne . A related machine, the IBM JX , was sold in the Japan, Australia and New Zealand markets. The PCjr chassis is made entirely of plastic, unlike the all-steel chassis of the IBM PC. A 5.25" front bay allows the installation of a 180/360K floppy disk drive. The internal floppy drive was a half-height Qume 5.25" unit; IBM also used these drives in
17947-424: Was not emphasized by users or manufacturers, as the systems' limited RAM capacity, graphics abilities, and storage options had a more perceivable effect on performance than CPU speed. For low-price computers, the cost of RAM memory chips contributed greatly to the final product price to the consumer, and fast CPUs demanded expensive, fast memory. As a result, designers kept clock rates only adequate. In some cases, like
18084-485: Was reportedly high until demonstration machines were available, at which point interest dropped steeply. Dealers reported that consumers disliked the price, keyboard, and limited memory, and retailers that sold primarily to business customers did not know how to market it. The press soon reported that the PCjr could embarrass IBM, with executives reportedly worrying about demand. Stores began discounts while vendors slowed plans to release products. IBM admitted that demand for
18221-417: Was that while those TV-monitors had difficulty displaying the clear and readable 80-column text that became the industry standard at the time, the only consumers who really needed that were the power users utilizing the machine for business purposes, while the average casual consumer would use the system for games only and was content with the lower resolution, for which a TV worked fine. An important exception
18358-474: Was the Radio Shack TRS-80 , the first mass-marketed computer for home use, which included its own 64-column display monitor and full-travel keyboard as standard features. This " peripherals sold separately" approach is another defining characteristic of the home computer era. A first-time computer buyer who brought a base C-64 system home and hooked it up to their TV would find they needed to buy
18495-501: Was the TI-99/4 , announced in 1979 with a 16-bit TMS9900 CPU. The TI was originally to use the 8-bit 9985 processor designed especially for it, but this project was cancelled. However, the glue logic needed to retrofit the 16-bit CPU to an 8-bit 9985 system negated the advantages of the more powerful CPU. Another exception was the Soviet Elektronika BK series of 1984, which used the fully-16-bit and powerful for
18632-424: Was the first place to see the appearance of new retail stores dedicated to selling only computer hardware, computer software, or both, and also the first place where such stores began to specialize in particular platforms. By 1982, an estimated 621,000 home computers were in American households, at an average sales price of US$ 530 (equivalent to $ 1,673 in 2023). After the success of the Radio Shack TRS-80 ,
18769-453: Was used then there would be six buffers). The command to swap or copy the buffer typically applies to both pairs at once, so at no time does one eye see an older image than the other eye. Quad buffering requires special support in the graphics card drivers which is disabled for most consumer cards. AMD's Radeon HD 6000 Series and newer support it. 3D standards like OpenGL and Direct3D support quad buffering. The term double buffering
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