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Ray Holt and the Lost History of the First Multi-Chip Microprocessor

During a Zoom meeting of the Computer History Museum’s (CHM) SemiSIG earlier this year, our fearless leader Doug Fairbairn mentioned that he was having trouble contacting Ray Holt to arrange a recording of his oral history. CHM’s SemiSIG records oral histories of past and present luminaries in the semiconductor industry, and Holt’s history is a rich one. After getting his EE degree at Cal Poly in 1968, Holt joined the team at Garrett AiResearch that designed the CADC (Central Air Data Computer), which was the world’s first digital electronic flight computer. It was an electronic update of the electromechanical CADCs developed by Kollsman and Bendix during the 1950s to help pilots manage military jet aircraft. Garrett AiResearch’s CADC was slated to be installed in the US Navy’s F-14 Tomcat swing-wing fighter jet, where it would electronically manage the aircraft’s various control surfaces.

The heart of the Garrett AiResearch electronic CADC was quite possibly the world’s first multi-chip microprocessor, and you have likely never heard of this microprocessor milestone because it was a classified project for 30 years. Finally, in 1997, Holt managed to win approval to get the CADC declassified when the officer in charge of the F-14 program at the Pentagon realized that he was discussing a project that occurred before his birth. That’s the only reason we know the details about the F-14’s CADC today.

I published an article about Holt in EEJournal last year (see “Ray Holt and the CADC – The World’s First Military Digital Flight Computer”), based on his autobiographical book The Accidental Engineer, and I still had his telephone number and email address handy. So, I piped up during the SemiSIG Zoom call and said I’d be happy to record Holt’s oral history for CHM. Holt and I recorded a 2-hour oral history on May 26, and CHM has now posted the resulting video on YouTube (click here for the video) and a written transcript of that video (click here for the transcript). In this oral history, Holt and I discuss the development of the CADC, well covered in my previous article, and the many fascinating things he did after that project.

Holt left Garrett AiResearch in 1971 and joined AMI. During the CADC project, he’d worked with AMI to define the CADC chipset, and AMI eventually manufactured the NMOS CADC ICs. According to Wikipedia, Grumman made 712 F-14 fighters. Even counting prototypes, training equipment, and spares, the entire run of dual-redundant CADC chipset ICs needed for the F-14 project represented a fairly small manufacturing run, when compared to the unit volumes that semiconductor makers usually deal with. The wafer run for the CADC was so small that AMI refused to bid on the manufacturing contract, so Garrett AiResearch bought AMI and owned the semiconductor maker for at least the duration of the F-14’s CADC project. (Many years later, in 2008, On Semiconductor absorbed AMI.)

At first, Holt worked on single-chip calculator ICs at AMI. Calculator chips were all the rage during that time. Then, after Intel announced the world’s first commercial, single-chip microprocessor in November 1971, AMI manager Ken Rose organized a microprocessor group. With his prior CADC design experience, Holt fit right into this new group. He worked on the design of two proprietary and obscure AMI microprocessor architectures: the 3-chip 7200 and the microprogrammable, 2-chip 7300. AMI then discovered that there was more to making microprocessors than merely making the silicon. The microprocessor vendor also needed to develop companion software and provide training. Consequently, AMI’s management got cold feet, decided there was no future in microprocessors, and disbanded the company’s microprocessor group. All 25 people in the group were terminated, including Holt.

At this point in his career, Holt had more microprocessor design and application experience than most of the engineers in the semiconductor industry. He’d developed an embedded microprocessor chip set for the CADC and taught it to fly a swing-wing fighter jet. He’d developed two more microprocessor architectures at AMI after that. Holt joined forces with a laid-off AMI programmer named Manny Lemas, and together they hooked up with a Palo Alto consulting firm owned by Lowell Amdahl, Gene Amdahl’s brother. Holt and Lemas conducted some training classes for Intel’s microprocessor group, but the training gig didn’t dovetail well with Lowell Amdahl’s business model, so Holt and Lemas took that training business, with Amdahl’s blessing, and started their own consulting firm – Microcomputer Associates – in 1974.

While training engineers to use microprocessors in 1974, Holt and Lemas realized that there just wasn’t a lot of good engineering information available about microprocessors. Consequently, Microcomputer Associates started publishing a newsletter titled Microcomputer Digest. One of the technicians at Microcomputer Associates, Darrell Crow, had a journalism background, and he happily took the lead on Microcomputer Digest. Microcomputer Associates published Microcomputer Digest for two years and eventually had 1000 subscribers paying $60 per year. Back then, $60,000 per year was a good-sized annual revenue for a small newsletter. For comparison, I started at HP as a design engineer back in 1975 with a starting salary of $10,400 per year. Eventually, Microcomputer Associates decided it did not want to be in the publishing business. The company failed to interest another publisher in taking over the subscriber base, so it shut down Microcomputer Digest in late 1976.

By then, Microcomputer Associates had started making its own microprocessor board, called the Jolt, which was based on MOS Technology’s immensely successful 6502 microprocessor. The Jolt was quickly followed by accessory cards, including I/O cards, RAM cards, and a music card. Jolt customers requested even more features and capabilities, so Microcomputer Associates developed the Super Jolt. Eventually, Synertek, which had become a second source for the 6502, decided to start a systems division. Instead of starting the division from scratch, Synertek bought Microcomputer Associates, which was having cash-flow problems because of its board-making business. A month later, Honeywell bought Synertek, so Holt and Lemas became Honeywell employees. It was not a good marriage, and Holt left Honeywell in 1980.

Holt restarted his consulting business, opened a retail computer store, and ran it for about ten years. After he tired of selling IBM PC clones, he started a Web design business and closed his retail location. He’d discovered early on that you don’t need a brick-and-mortar store if your business is in cyberspace. Holt retired (for the first time) in 2000, went to Oklahoma, and spent four years researching his Cherokee ancestors.

A chance phone call from a friend living in Mississippi drew Holt to that state. Along the way, he did a bit of consulting from his RV. Holt’s friend in Mississippi ran a Christian Ministry and supported twelve additional rural ministries. The friend told Holt, “All of them are having computer problems. Would you stay a few weeks and go to each one and fix their problems?” Holt took on the task and never left Mississippi. He still lives there.

Teaching STEM (science, technology, engineering, and math) subjects to disadvantaged kids has kept Holt in Mississippi. “It’s hard to get away from it when you know you can help them,” said Holt. He taught a Saturday programming class for robotics and his student team went to a world robotics competition. Holt realized he’d latched onto an idea that was much bigger than himself and he seems to have relished the challenge. During his oral history, Holt said, “…it was 2014, and I’ve been doing that since. So, we do after-school programs, camps, and a lot of teacher training competitions. We’ve trained about 500 STEM teachers so far, and work directly with them, and with about 3000 students.”

Today, Holt’s vision has grown even larger. He envisions a Mississippi Institute of Technology, although he admits that those initials are already taken. He wants to build an actual campus on 300 acres, designed to teach all aspects of STEM from 4th to 12th grade. Here’s a visualization of the campus:


Mississippi Institute of Technology campus, as envisioned by Ray Holt. Image credit: Ray Holt

The idea is to develop a home-grown, 21st-century workforce for Mississippi, with employable skills driven by industry requirements, and with an emphasis on hands-on learning. Holt has seen how kids’ faces light up when they’re learning while doing and he seems thoroughly hooked. Today, Holt is president of STEM Advancement, Inc, a 501c3 organization dedicated to the advancement of STEM education. If you’re interested in Holt’s vision, please check out that Website.

This article only lightly touches on many aspects of the two-hour oral history recorded for CHM. It’s not possible to compress two hours of energetic conversation with Ray Holt into one EEJournal article without suffering severe compression artifacts. If you’re not familiar with this part of microprocessor history, dig into Holt’s oral history in the video or transcript version. You’re in for quite a ride.

For more information about the microprocessor chip set designed for the F-14 CADC, see Ray Holt’s Web site: World’s First Microprocessor.

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