Technology

Many home computers were superficially similar. Most had 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 the form of cumbersome "sidecar" system, 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 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 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 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 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 was the TI-99 series, 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 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 CPU's and 2–4 MHz for Z80 based systems (yielding roughly equal performance), but this aspect 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. So designers kept clock rates only adequate; in some cases like 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 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 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 datacassette drive and could perform much like 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 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 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 the Atari 1040ST (not the 520ST), the Commodore Amigas, and the Tandy 1000s 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 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 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 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 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. Also, 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 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 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 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 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.

PCs at homeedit

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 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 computerists. 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 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 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, 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, and 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 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 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 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 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 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 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 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 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 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 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 a turbo NEC V40 CPU (uprated 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 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 a rate such that 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, multifunction 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 the viability of PC/DOS computers as alternatives to specially-made computers and game consoles for the home.

High performanceedit

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 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, a first for a standalone 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 the base Amiga 1000) up to 1024 KB (1 megabyte, 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 Apple Macintosh, but at a list price of US$2495 (equivalent to $5,900 in 2019), the Macintosh itself was too expensive for most households. The Commodore 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.

MSXedit

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 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 a great deal of software support from the traditional Japanese publishers of game software, but never garnered such support from publishers of productivity applications. Microsoft did, however, produce a special version of the BASIC programming language that ran under MSX.