Few people have heard of it, yet many consider John Blankenbaker's KENBAK-1 to be the first commercial personal computer.
Recreating the First Microprocessor-Based Calculator
By James Grahame
In 1969, Japanese electronics manufacturer Busicom approached a little startup called Intel to develop a chipset for their new 141-PF electronic printing calculator. Intel's solution was the world's first single chip microprocessor -- the tiny Intel 4004 -- which powered the Busicom machine to groundbreaking success in 1971.
37 years later, Bill Kotaska has crafted a replica of this historical machine capable of running the software from the original Busicom ROMs. He even went to the trouble of buying an old calculator of approximately the right vintage and rearranging the mechanical switches to match the original Busicom layout.
The printer mechanism was originally manufactured by Epson, and Kotaska was able reuse one from an old Monroe 1330 printing calculator, although the lack of a full schematic diagram made it tough for Kotaska to figure out exactly how it was supposed to interface with the logic circuit. He eventually got it running and the result is a stunning bit of retroputing history.
Busicom sold 100,000 Intel-based calculators before finding themselves in financial trouble. Intel used this misstep to their advantage and bought back the rights to the chip for non-calculator applications. The rest is history.
The 4004 was a tiny 4-bit processor with an 8-bit wide instruction set. It was capable of running at speeds up to 740 kHz and could address up to 4K of ROM and 1280 x 4bits of RAM, although the accompanying MCS-4 chipset included a tiny 256 byte mask-programmable ROM and 340 byte RAM chip. It seems laughable by todays standards, but those meager specifications were enough to open up a brand new world of programmable logic capable of replacing extremely complicated and expensive electromechanical systems.
Intel followed the success of this little 16 pin chip with the 8008, a 3,300 transistor 8-bit chip that was introduced in late 1972. The company went on the have a string of successes throughout the 1970s, but it was the incorporation of their processors into the IBM-PC lineup in the 1980s that enabled them to become the largest processor manufacturer in the world.
Incidentally, original 4004 chips are now highly collectible and a rare gold-white-grey chip like the one shown here can change hands for well over $1000. That said, I'd much rather have been given $1000 of Intel stock in the early 1970s - it'd be worth over $500,000 today -- enough for a massive stack of vintage chips.
