Imagine a world in which all cars are like the Toyota Prius: four-door midsize hybrids. Sure, they aren’t bad cars, you can paint them any way you want and even modify some parts, but in the end you still just have a generic Toyota with a funky paint job.
That’s the world of personal computing today. It doesn’t matter if you’re running Windows, Mac OS, or Linux. Your machine is almost certainly using Intel chips at its core and almost everything else is fairly generic—even the world’s greatest case mod with water-cooled dual-Xeons and quad-SLI graphics is just a really fast PC.
This was definitely not the case 35 years ago. A quick tour of the Computer History Museum in Mountain View, CA, reveals machines that were as varied and unique as the companies that made them.
The microprocessors, if there even was one, were supplied by Intel, MOS, Zilog, RCA, or any number of other companies. Memory was static, dynamic, and shift-register. And without the Internet, programs were loaded from paper tape, punched cards, cassette tape, floppy disks, cartridge, or even manually switched in by hand.
In the following pages, we take a close look at some of the most influential personal computers of the past 40 years. From pre-microprocessor machines to the venerated IBM PC, each of these systems contributed in some way to the modern personal computing era.
Widely considered to be the first true personal computer, John Blankenbaker’s $750 Kenbak-1 had almost everything a modern computer has: I/O (lights and switches,) memory (256 bytes of shift-register memory), and a full set of op-codes. Missing were storage and an actual CPU; the Kenbak pre-dated the microprocessor by more than a year so the logic was implemented in discrete transistor-to-transistor logic (TTL).
The machine, designed by engineer John Blankenbaker, sold for $750 from a tiny ad in the back pages of Scientific American magazine at a time when a new Ford Pinto could be had for a cool $2,000.
Only a few dozen were ever built and many were used to train mainframe programmers.
RAM 256 Bytes CPU No CPU (logic in TTL) Supporting OS None Predecessor Early mainframes Successor All other PCs Notable Firsts By most accounts this was the first PC
Xerox’s Palo Alto Research Center (PARC) was the source of numerous computer innovations including the mouse and the windowed graphical user interface. The company’s Alto system was never a commercial product but it did incorporate most of the aspects one expects from a modern computer: mouse, hard drive, networking, and a windowed GUI represented on a bitmapped screen.
Xerox built thousands for internal use and donation to various educational institutions.
Both Bill Gates and Steve Jobs were given demonstrations of the Alto’s (and the later Xerox Star) user metaphor and both went on to design their own versions for commercial sale.
Xerox eventually tried to capitalize on the technologies with the Xerox Star, released commercially in 1981, but the system was expensive and sold poorly.
RAM 64K-256K words (128K-512K bytes) CPU Proprietary 16-bit Supporting Operating Systems Alto Operating System Predecessor Various bits of Xerox PARC research Successor All GUI based PCs Notable firsts First GUI, first Mouse
In early 1974 there weren’t many microcomputers available, but in March of that year, SCELBI (Scientific, Electronic, Biological) introduced its $550+ 8 series, based around the Intel 8008 microprocessor. Offered were the 8h hobbyist kit and the 8b business computer.
In addition to the machines, SCELBI produced some programming books and software. When the company realized that the documentation and programs made more money than the machines, it quickly adjusted its business model and abandoned hardware sales.
RAM 1K to 16K CPU ~.5MHz Intel 8008 Supporting Operating Systems None Predecessor Early mainframes/Mini-computers Successor Other Intel-based personal computers Notable firsts First microprocessor-based hobbyist PC
Radio Electronics and Popular Electronics magazines used to engage in contests of one-upmanship for front-cover projects. In July 1974 Radio Electronics’ cover featured one of the first CPU-based PCs, the Mark-8 minicomputer kit. For about $50 you got an instruction booklet and a few circuit boards.
After gathering $250 or so in components like RAM chips, resistors, capacitors and the expensive 8008 microprocessor and then doing a whole bunch of soldering the buyer would, hopefully, end up with a real computer running at .5 MHz with 256 bytes of RAM and some basic I/O.
Hobbyists found many ways to expand this system but the 8008’s address limit of 16K ultimately proved a barrier, especially when alternatives existed such as Popular Electronics’ response: the Altair 8800.
RAM 256 bytes to 16K CPU .5MHz Intel 8008 Supporting OS None Predecessor None Successor Various Mark-8 homebrew iterations Notable Firsts First popular computer kit
MITS Altair 8800
In 1975, responding to Radio Electronics’ Mark-8, Popular Electronics debuted the Altair 8800, an Intel 8080-based machine sold as a 1K kit for $500.
Although the Altair wasn’t really the first PC, what it lacked in primacy it made up for with its ability to generate excitement. A soon-to-be Harvard dropout named Bill Gates was so taken by the machine that he and some friends felt compelled to write a version of BASIC for it. This landed them on the MITS staff and, eventually, led to the founding of “Micro-Soft” - later Microsoft.
The machine also defined the first standard Personal Computer bus architecture, the S-100 bus, and inspired a new generation of personal computing pioneers; the number of companies formed and fortunes made because of the Altair is simply amazing although few of those made it to today.
RAM 256 bytes to 64K CPU 2 MHz Intel 8080 Supporting OS MITS DOS, CP/M, and others Predecessor Mark-8 and other early PCs Successor IMSAI 8080 and all other S-100 machines Notable Firsts First S-100 bus machine, first widely popular PC
The KIM-1 was designed to showcase the new MOS 6502 microprocessor. The chip was introduced at $25 per unit when the cost of Intel’s 8080 was nearly $200 in bulk. In spite of the price, the 6502 was for real, as the KIM-1 proved.
MOS was quickly bought up by Commodore who used the chip in their Commodore PET line of computers.
A couple of guys named Steve quickly built a single-board computer using the new chip and then named it after a fruit. Over time, it was incorporated into machines from Atari, Ohio Scientific and more.
The 6510, a later version in the 6502 family, powered the popular Commodore 64.
RAM 1K CPU 1 MHz 6502 Supporting OS None Predecessor None Successor All other 6502-based machines (Apple, Commodore, Atari, etc.) Notable Firsts First use of the 6502 computer
With the overnight success of the MITS Altair 8800, others quickly geared up to tap into the market. IMS Associates Incorporated (IMSAI) quickly reengineered a pre-production machine to conform to the new S-100 standard while simultaneously fixing a number of obvious flaws in the MITS design.
The result was the IMSAI 8080; the first Personal Computer clone and a movie star to boot.
The IMSAI 8080 conformed to the Altair’s standards while upgrading the front panel, case and power supply with far more robust parts.
In the end the IMSAI outsold and outlasted the Altair; proving that you don’t have to be first to succeed.
RAM 1K-64K CPU Intel 8080 Supporting OS IMSAI DOS, CP/M, and others Predecessor Altair 8800 Successor Later S-100 systems Notable firsts First S-100 clone
In 1976 Steves Jobs and Wozniak were both active in the tight-knit Silicon Valley computer hobbyist scene. Inspired by what they saw at various Homebrew Computer Club meetings, they sold their toys (a calculator and a van) for the capital to hand-build the earliest Apples, launching an industry icon.
The Apple I wasn’t particularly revolutionary but it was very well engineered, included video circuitry and it was relatively inexpensive which helped it catch on.
The first run of 200 or so units sold out quickly (at $666.66 apiece) and convinced Apple to build and sell the Apple ][ which, with a little bit of help from the first “Killer App,” revolutionized the Personal Computer market.
RAM 4K CPU 1MHz 6502 Supporting OS Cassette BASIC Predecessor KIM-1 and early 6502 systems Successor Later Apple systems Notable firsts Apple’s first computer
Until the Sol-20 hit the scene, a personal computer was pretty impersonal. The best a user could hope for was rows of switches and lights or a hex keypad and a handful of LEDs. It took a lot of work to make those machines do things which meant that they were reserved for only the geekiest of users.
Lee Felsenstein, the yardstick-wielding moderator of Homebrew Computer Club meetings changed that with his S-100 based Sol-20. This machine, sold as a kit or fully assembled, was the first “out of the box” PC, sporting a keyboard, video circuitry as well as ROM based software available at power-up.
When plugged into a TV set (with an RF Modulator) or an inexpensive monitor it was ready to go.
RAM 4K-64K CPU 2MHz Intel 8080 Supporting OS SOLOS, CP/M, Northstar DOS, and others Predecessor Altair 8800 Successor Other integrated computers (Apple, Commodore, etc.) Notable firsts First integrated machine with keyboard, video, etc.
Commodore Pet 2001
The $600 Commodore PET was the first fully integrated “appliance computer” that included everything needed out of the box. It was effectively an expansion of the earlier KIM-1 with video logic added to drive the internal monitor.
The PET was a popular machine, especially in the educational market, possibly because it was built into an amazingly sturdy steel case.
The system was also attractively designed although some of that came at the expense of functionality. One early complaint was the chicklet-style keyboard (designed to use Commodore calculator keys) which was a far cry from the full-size keyboards included with the PET’s competitors. The original issue of 8K (a 4K model was quickly dropped) of included RAM was also a problem.
These deficiencies, as well as others, were addressed with later updates and helped the Commodore PET line attain high levels of popularity in the US as well as in Europe.
RAM 8K CPU 1MHz MOS 6502 Supporting OS Built-in BASIC Predecessor KIM-1 Successor Other Commodore machines Notable firsts First fully integrated “appliance” computer
TRS-80 Model I
Tandy/Radio Shack produced one of the earliest personal computers and, for a while, the “Trash-80” systems were very popular in a crowded market. The TRS-80 competed well with the Apple ][ and Commodore PET and earned a loyal following among the limited number of home computer enthusiasts. The Radio Shack system was based on the Zilog Z-80 processor (an Intel 8080 clone, with a few upgrades) and used a modified Tandy television as its monitor.
The Model I was felled by the FCC for its RF interference but was followed by a series of models designed to serve the home and business PC markets.
Tandy Ultimately succumbed to the IBM PC steamroller and produced PC work-alikes and clones after axing the venerable TRS-80 line.
RAM 4K-48K CPU 1.78 MHz Zilog Z80 Supporting OS TRSDOS Predecessor None Successor Several more models in the TRS-80 line Notable Firsts First Tandy/Radio Shack computer
After the Apple I, Steve Wozniak designed a new version of his baby which addressed several of the original’s biggest shortcomings. For one, the new machine was a complete system. The power supply and keyboard came standard! With Integer BASIC and a hardware monitor in ROM the Apple ][ was a “turnkey” system – turn it on and it worked – which had suddenly become de-rigueur for the industry.
A combination of an open architecture and brilliant marketing helped the Apple computer quickly become a household name.
With the advent of VisiCalc, the first spreadsheet, the Apple also turned the business world on its head as people snuck them in to work to compete with the Big Iron.
RAM 16K-48K CPU 1MHz 6502 Supporting OS Apple DOS Predecessor Apple I Successor The rest of the Apple line (][+, ///, ///+, IIgs, //c, etc.) Notable Firsts First mass-market Apple
The Exidy Sorcerer was an early Z80-based system that tried to bridge the gap between lower-end home/educational machines and the S-100 business world.
Exidy offered an S-100 expansion chassis that could be plugged in to their base system to turn it into a full-fledged S-100 box capable of using the cards and running the software of the likes of the IMSAI and Altair.
The Sorcerer was likely the first personal computer with a cartridge slot for at-boot software. In an odd twist, cartridges used hollowed out 8-track tapes to hold the circuit boards and ROMs. Software from BASIC to word processors was available via these cartridges.
Although it was a well built and highly functional machine with a good keyboard, built-in software monitor and good expandability it wasn’t nearly popular enough to live on.
RAM 8K-64K CPU 2MHz Zilog Z80 Supporting OS CP/M Predecessor None Successor None Notable Firsts First cartridge-based PC
Atari became a household name with their arcade games and built on that reputation with home gaming systems including Pong and the Atari 2600 game console.
It was inevitable, then, that Atari further capitalize on their name by entering the burgeoning home computer market. They did so in 1979 with the introduction of the Atari 800 and its little brother the Atari 400.
The Atari systems were similar to their competitors, the Commodore Pet and Apple ][, in their use of the 6502 processor, but Atari’s gaming roots resulted in the inclusion of several custom chips to control sound and graphics making the Atari 800 an early gaming masterpiece.
This helped sell the machines while various productivity applications such as word processing, database and spreadsheets helped them find a solid following in the home market.
RAM 16-48K CPU 1MHz 6502 Supporting OS Atari DOS Predecessor Prior Atari products Successor A whole line of later Atari computers Notable Firsts Atari’s first home computer
The Apple /// represents Apple’s first real failure.
With 128K of RAM, a built-in floppy drive and optional hard drives this Apple was intended to be a true business computer but early design flaws and a high price kept it from success while IBM came in and stole the show.
The machine was sold without a fan which made it overheat causing the main-board to warp. One official Apple solution promoted percussive maintenance to fix the issue - users were advised to drop the machine several inches to re-seat loose RAM chips.
By the time Apple had addressed the early flaws with the introduction of the improved Apple ///+ the PC was the dominant player in the business market and Apple was on the sidelines.
RAM 128K CPU 1MHz 6502 Supporting OS SOS, CP/M, Apple DOS Predecessor Apple ][ Successor Apple Lisa, Mac, etc. Notable Firsts Apple’s first misstep
Adam Osborne did lots right when he bundled his computer with all the useful applications—word processing, spreadsheet, database, programming etc.—and sold it for a reasonable price.
He also made computer marketing history when he pre-announced the “Next Big Thing” way too soon and killed the revenue stream he needed to complete development on that next big thing.
The Osborne “luggable” was an evolutionary dead-end (which didn’t prevent dozens of other companies from Compaq to Zorba from copying the form-factor) but it did show that people wanted to be able to take it with them and it proved that hardware was only a means to software.
RAM 64K CPU 4MHz Z80 Supporting OS CP/M Predecessor Early CP/M machines Successor All suitcase portables, later Osborne models Notable Firsts First suitcase portable, first system bundled with full suite of applications
Epson’s HX-20 was the world’s first effective and popular notebook computer. It could run for 50 hours on its internal battery, had a real keyboard, built-in productivity applications, and mass storage. It even had a built-in printer!
Sure, the 4x20 character LCD was a bit limiting and the tape drive was slow, but this was a real computer in a sub-4lb package that worked!
The ability to add ROMs for additional functionality made this machine popular for targeted applications like engineering and data gathering.
The system also presaged the laptop form-factor, minus the clamshell screen.
RAM 16K CPU .6MHz Hitachi 6301 Supporting OS CP/M Predecessor None Successor Later notebook formfactor computers Notable Firsts First notebook computer
The IBM PC was one of the most anticipated arrivals to the personal computer era. IBM countered its usual process to produce the PC quickly using mostly off-the-shelf parts.
Almost all modern PCs, even those running Mac OS and UNIX flavors, are descendants of this venerable architecture. Although IBM entering the Personal Computer market had a profound effect on how computers were accepted in business, the biggest impact was Microsoft licensing DOS and BASIC to IBM. Bill Gates was able to wrangle an open agreement that allowed Microsoft to eventually sell these products to other vendors.
As soon as the clones started coming Microsoft had a ready market that just kept growing.
RAM 16K-640K CPU 4.77MHz 8088 Supporting Operating Systems PC DOS, CP/M, UCSD-P Predecessor IBM 5100 and various early PCs Successor IBM PC XT and the rest of the line Notable firsts First successful IBM Personal Computer
The Commodore 64 is one of the most recognized computers ever built. It should be; it holds the world record for the most units sold of any computer. What the C64 lacked in technology it made up for in popularity and price. This machine helped cement the idea of a “home” computer when that concept was almost as alien as a personal aircraft carrier and it did so because the machine was both affordable and accessible.
While a few Commodores were used for productivity most ended up as game systems while an entire generation of software engineers got their programming start writing BASIC code on a C64.
RAM 64K CPU 1MHz MOS 6510 Supporting OS Built-in BASIC and CP/M (with additional hardware) Predecessor Commodore PET line Successor Commodore Plus/4, Amiga, and later machines Notable Firsts Best-selling PC ever
Franklin Ace 100
The nascent personal computer industry had never addressed copyright issues for hardware and firmware designs until Franklin copied the Apple ][ (down to the ROMs) and started selling them at a discount.
Apple quickly sued and, in 1983, won a judgment against Franklin in a landmark court case. Franklin was then forced to reengineer their products and to reverse engineer Apple’s ROMs, but by the time they came out with their new machines it was already near end of life for the Apple ][ line, the PC was king and the Mac was out of the gate.
RAM 16K-48K CPU 1MHz 6502 Supporting OS Apple DOS Predecessor Apple ][ Successor Ace 1000, Ace 1200 Notable Firsts Caused the first software copyright lawsuit
A few guys from Houston got together to design the first true PC clone—on a placemat, no less! Sure, at nearly 30 pounds it wasn’t a lightweight, but it was “portable” and, most importantly, you could run Flight Simulator on it.
They reverse engineered the BIOS so as not to be stuck with IBM royalties or legal issues and quickly built one of the more successful computer companies.
In the long run they beat IBM to the punch in releasing a 386 based machine and they stuck with the ISA bus when IBM went to Micro Channel. For these reasons and others they outlasted Big Blue in the PC market.
RAM 128K-640K CPU 4.77MHz 8088 Supporting OS MS-DOS, CP/M Predecessor IBM PC Successor Later Compaq machines Notable firsts First black-box reverse-engineered IBM PC clone
IBM tried the home computer thing, too. Although the IBM PCjr was highly publicized and much anticipated, the reality of the machine was well below expectations.
Sure, it was a powerhouse as compared to the Atari’s and Commodores it targeted, but it also cost hundreds more and it came with a really crappy keyboard and awkward expansion via sidecars.
And, on top of that, it wasn’t 100% IBM PC compatible!
In the end, being a 16 bit player in an 8 bit home computer market wasn’t enough to save this little peanut.
RAM 64K-640K CPU 4.77MHz 8088 Supporting OS IBM PC DOS Predecessor IBM PC Successor None Notable firsts First IBM home computer
IBM PC XT
A hard drive and an OS with subdirectories don’t seem like much now, but in 1982 these were hawt! IBM and Microsoft weren’t the first to deliver either technology but they were the first to really mainstream it. Before the XT, hard drives were a luxury. After the XT, they were expected.
IBM also killed the cassette port, added slots and beefed up the power supply in recognition of the real users of their technology and in acceptance of their earlier “misunderestimation” of the PC market.
RAM 64K-640K CPU 4.77MHz 8088 Supporting Operating Systems PC DOS, CP/M, UCSD-P Predecessor IBM PC Successor IBM PC/AT Notable Firsts First IBM PC with a hard drive
Introduced in a now-world-famous Super Bowl ad, the Apple Macintosh wasn’t the first GUI PC — it wasn’t even Apple’s first GUI PC— but it was the little computer that could and it sparked a revolution in personal computer design while redefining people’s expectations of PCs.
When introduced, the Macintosh was underpowered with only 128K of RAM and a slow Motorola 68000 processor, but popular technology and rapid-fire upgrades helped it hold its own.
The Mac not only represented a new technological age for Apple, it defined a break from their “open architecture” standards of the Apple ][ era. With the Mac Apple rebuffed the aftermarket and saw their market share decline dramatically.
RAM 128K CPU 8MHz Motorola 68000 Supporting OS MacOS Predecessor Xerox Star, early Apples Successor All later Macs Notable Firsts First “affordable” GUI-based PC
The PC/AT introduction was the last time IBM managed to set the PC pace. Its Intel 80286 processor was a true 16 bit unit which meant that IBM had to redesign the bus for 16 bit addressing. The bus quickly became the industry standard and was soon named as such.
The ‘286 also upped RAM limits from 1MB to 16MB and brought about new levels of suffering with Expanded and Extended memory management.
Over-clocking was briefly possible with the earliest ATs until IBM redid the ROMs to prevent that. Other vendors, however, were more accommodating.
Either way the AT brought forth enough power for Microsoft to run a new DOS shell with technology borrowed from Xerox PARC.
And thus Windows was born.
RAM 256K-16MB CPU 6MHz 80286 Supporting Operating Systems IBM PC DOS, CP/M and others Predecessor IBM PC XT Successor IBM PS/2 line Notable Firsts First IBM 16 bit PC and Bus
A look back at these old machines shows the clear path of Moore’s Law. Since the release of the IBM PC/AT, the personal computer has grown faster and microchips have shrunken smaller by orders of magnitude. The antiques we’ve showcased may be considered slow and crude by today’s standards but they all contributed, even if only a little, to the PCs we use today.
In the early days of personal computing, users had any number of options for loading programs and for keeping their data safe. Floppy and hard disks were common, but so was paper tape and cassette tape. Less common were micro-cassette tape, bubble memory, and even “floppy ROMs,” which were thin, plastic records sent with some computer magazines. And speaking of ROMs, there were the standard ROM chips plugged into boards but many manufacturers put them into card-edge packages and tucked them into plastic cases (cartridges.)
Examples: 5.25” 30 MB hard drive, 8” floppy, 5.25” floppy, 3.5” floppy, Coleco Adam High Speed Digital Data Pack, Cassette Tape, Micro Cassette Tape.
All of these and more were used on early computers. Most were slow and fairly clunky, but they were far better than re-keying programs every time you rebooted.
The total capacity of these represents less than 1/20th of one CD ROM.
Solid State Media
Examples: 2K ROMs, ROM Board/bare Exidy Cartridge, Atari Cartridge, Commodore 64 Cartridge, TI 99/4a Cartridge, Intel 1702 EPROM (256 bytes), Exidy Sorcerer Cartridge (in a hollowed out 8-track tape case) Coleco Adam/Colecovision cartridge.
Cartridges and ROMs were used to provide ready code at boot so that the computer was useful as soon as power was applied.
Examples: Paper tape, Interface Age Floppy ROM, Punched cards.
Paper tape was widely popular for the earliest computers due to the easy availability of used Teletypes. These operated at 110 baud (10 bytes per second) which meant that a typical 8K program would take nearly 15 minutes to load! Most other media were faster, but not always by much.
Bill Gates Asks Hobbyists to Pay Up
Early users groups from coast to coast (the SiliconValley Homebrew Computer Club being the most famous) were venues for geeks to gather, demonstrate their knowledge, and share their inventions. Some folks demonstrated their new computers, some shared renditions of old tunes played on an Altair computer, and some shared software. Sometimes it was software they wrote and sometimes it was software that someone else wrote.
In one notable early incident, a regular at the Homebrew Computer Club obtained a copy of Altair BASIC on paper tape. Prior to the next meeting he made dozens and dozens of copies, which he freely distributed to other attendees.
So, in 1976 Bill Gates had a problem. He was making software that everyone loved but that few were bothering to pay for. In frustration, Gates penned an “Open Letter to Computer Hobbyists,” which was published in the Homebrew Computer Club newsletter and elsewhere. In the missive he explained that the unauthorized copying of software was theft and that doing so inherently discouraged developers from producing good software.
He explained that only about 10 percent of Altair owners had bought BASIC (although all seemed to own it) and that he and his staff were effectively working for $2 an hour producing quality software that the hobbyist community clearly valued.
The letter sparked some harsh exchanges, including a more pointed follow-up letter by Bill Gates, and ultimately started the discussion about software piracy. This discussion has, of course, picked up steam and continues to this day.
The Big Boys of Computing’s Early Days
Before computers were staple appliances in the home, they were the domain of corporate offices, research laboratories, and even government bases. Like the one in Adam West's batcave, these machines were mechanical giants, taking up entire rooms and prominently displaying analog parts. The Computer History Museum in Mountain View, CA, hosts a grand collection of these computing artifacts, and here are three of our favorites.
SAGE (Semi-Automatic Ground Environment) Air Defense Computer
The SAGE display represents a small portion of the typical 300-ton installation of a computer used by the military to detect threats. These vacuum tube computers were deployed in redundant pairs at 27 linked installations throughout North America with the goal of tracking Soviet bombers during the Cold War. The SAGE project, started in 1954, included forward-looking technology such as modems, networking, and even light guns. The software driving the machines was amazingly advanced for the day, as well. Look closely, and you can even see a cigarette lighter built into the console!
IBM System 360
The IBM System/360 represents a major turning point in computer history. Prior to the 1965 introduction of the System/360 a computer upgrade meant a complete rewrite of all software. With the 360, IBM unified its computer architecture and permitted users to move up and down the line using the same software and operating systems. This enabled computing to penetrate deeper into industry worldwide and allowed IBM to dominate the market for decades.
Babbage Difference Engine
Charles Babbage (1791-1871) was, perhaps, the earliest computer pioneer. He designed numerous computing devices using Victorian-era technology, although the limits of that technology made it impossible for him to ever build any of his ideas. Fast forward 150 years and our technology proved his concepts viable with the creation of a working Babbage Engine. A functional replica of this analog computer sits in the lobby of the Computer History Museum, on loan until the end of this year.