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Gary Kildall: Some Rare CP/M History
These questions were posed via e-mail to ex-IMSAI Manufacturing Chief Engineer A. Joseph "Joe" Killian in 2001:

Gary Kildall's CP/M : Some early CP/M history
1976-1977


From Thomas "Todd" Fischer (originally posted to the comp.os.cpm newsgroup in 2001)

Fellow CP/M enthusiasts: Much of the early history of CP/M's roots has been lost over time. For those with an interest, I've always maintained that IMSAI was the first company to offer CP/M for 8080-based floppy systems. I had the honor of working with Gary Kildall in the later half of 1976 and early 1977 in implementing various permutations of rev. 1.2 and 1.3 on the IMSAI FDC and DIO floppy systems. IMSAI's former Chief Engineer Joe Killian e-mailed some answers to a number of questions I posed to him, an excerpt follows:  

Was IMS the second, or or was it the third company to license CP/M as an operating system?

Todd, Glenn Ewing bought one of our first 50 or so machines. He was on the faculty at the Naval Postgraduate school in Monterey at the time. We were promising an operating system at the time (and later hired Rob Barnaby to write it). Gary Kildall was also on the faculty at the Naval Postgraduate school, friend of Glenn's. (Glenn taught antenna field calculations, among other things.) When we failed to produce an operating system in a timely manner, Glenn started talking with Gary about CPM, which Gary had written for Intel under contract. It took several months of twisting Gary's arm to get Gary to port it to the 8080. The final success came when Glenn talked Gary into just separating the I/O from the rest of it, with Glenn promising to re-write the I/O module for the IMSAI 8080 (which he did). So CPM on the IMSAI was a joint effort between Glenn and Gary. It was only after all this that we arranged buying it from Gary. I still assume we were the first sale after his original Intel contract related to this.

This was all possible only after Glenn helped debug the FDC. Peter Olson had subcontracted to us to design the FDC end of '76, very early '77, following my general architecture. It basically ran, but had data errors all too frequently. We had not discovered the errors with our rudimentary testing. Glenn discovered them with test programs he wrote, and complained. After some considerable time trying to get Pete to solve the problem, Glenn offered and we accepted hiring Glenn to debug the FDC. I flew down to Monterey several times to loan him a scope & other logistics. He identified the problem and designed a solution. It worked. * That must have been late '77. Glenn was a quite thorough engineer and very methodical. That was a very different approach than I'd seen in Pete or other subcontractors we'd tried to use. We were delighted to hear Glenn express an interest in joining IMSAI, and he had the job lined up some months before his retirement from the Navy. He consulted in the meantime.

Glenn later did the VIO. We had started trying to design using the new Intel video controller, but when we got the first samples they ran only at 6.5V and had several other faults requiring work-arounds. We were in a hurry as always. Glenn examined the function and decided we could fit it on a board using separate parts. It was tight. Glenn did a great engineering job, and the VIO was cheaper than a board using the big video ASICs for a long time.


Was Seymour Rubenstein the first IMS personage to contact Gary Kildall? How did Seymour know of Kildall's talents? Clearly Seymour was not the first to contact Gary, though he did work out the business deal.

Clearly Seymour was not the first to contact Gary, though he did work out the business deal.

When was Rob Barnaby first brought on board with IMS, and by whom?

I expect mid to late summer '77. Rob was hired by Jan Vath, with some hesitation since he had been out of programming for a while. We talked about giving him a try, and if he didn't work out we could "Can his ass", phrase courtesy of Bruce  (Van Natta).  It floored both me and Jan Vath once when we were having lunch with Pete Olson, and there in front of Jan (my manager at the time) Peter Olson told me I should come and work with him, he could double my income. Later Pete was to co-found Octel.

Footnote:  Joe's salary at the time was about $2500 per month; trivial given his immense talent and contribution to the founding of IMSAI

*Note 1:  We were shipping the IMSAI FDC systems with CP/M by Spring of 1977, so Joe's memory is challenged with regard to this event. -trf