Dawn of the Personal Computer: From Altair to the IBM PC
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.
Special thanks to Erik Klein and the Computer History Museum for allowing us to photograph these artifacts from their collections.
Kenbak-1
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 Alto
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
Scelbi-8
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