Forgotten PC history: The true origins of the personal computer

The PC's back story involves a little-known Texas connection

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Hoff, then an Intel engineer, wasn't surprised. The CTC processor architecture "could go to 16,000 bytes of memory, and if you were going to spend that much on memory, then there was no sense in saving maybe $50 on the processor by moving it out of TTL," Hoff told Computerworld. Memory fell to a penny a bit in 1972, he recalled, so 16KB would have then cost $1,280 (around $6,700 today).

The 2200 debuts

CTC's TTL-based desktop personal computer, called the Datapoint 2200, was unveiled in 1970, with cassette tapes for 130KB of mass storage and 8K of internal memory. The first end-user sale (for 40 units) was to General Mills on May 25, 1970.

Following IBM's marketing model, the machines were leased: $168 monthly for a machine with 8K of memory, and $148 for 2K, with modems adding $30 monthly. RAM was not then available, so for internal memory the unit used recirculating MOS memory, with an access time of up to 500 microseconds for the first byte and 8 microseconds per sequential byte thereafter.

Aaron Goldberg, who in the 1970s was a researcher at IDC and is now vice president at Ziff Davis Media Market Experts in New York, remembered the Datapoint 2200 as one of the first single-user minicomputers, in the same class as the IBM 5320. "These were industrial-strength products. They were trying to downsize [mainframe] business applications," he recalled.

The logic unit appeared to be 8 bits wide, but the processor actually had to loop eight times to process a byte, noted Jonathan Schmidt, then with CTC and now vice president at Perftech Inc. in San Antonio.

Datapoint 2200
Production version of the Datapoint 2200.

At Intel, with the CTC chip on hiatus, development proceeded on the 4004, a 4-bit processor chip for Busicom, a now-defunct Japanese calculator firm that contracted with Intel before CTC, although work on the two projects began at about the same time. But after six months, Seiko Holdings Corp., another Japanese firm, expressed interest in using CTC's 1201 chip for a scientific calculator, and Intel resumed development on the CTC chip. The delay let the 1201 designers upgrade from a 16-pin to an 18-pin package.

CTC had also given a second-source contract to Texas Instruments Inc. Delivered in late 1970 or early 1971, the TI version of the 1201 chip never worked well, and the project was abandoned, Frassanito recalled. The Computer History Museum interviewees said that it was inadvertently sabotaged when TI used an initial specification -- produced for CTC by Intel -- that proved to be flawed.

Datapoint 2200 blueprint

Blueprint of the Datapoint 2200 enclosure, showing the crowded interior.

Click to view larger image.

Intel's 1201 chip was delivered to CTC in late 1971, but by then CTC was developing the Datapoint 2200 II, which ran much faster and supported a hard drive, and CTC's management was not interested in a chip that it now considered obsolete. Outvoting Roche, who Frassanito said was white-faced with shock at the decision, they dropped the project and abandoned the 1201 chip's intellectual property to Intel.

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