Some Processor Tech history

This page last updated jan 06 2010.

Summary:: In June-July 2004 in the comp.os.cpm Usenet newsgroup, there was a number of discussions of Persci floppy drive adjustments, The Cromemco 16FDC floppy controller, and of Processor Technology Inc. (an early S-100 company which used the drives. The notes below are a summary of Processor Tech discussion, responses by others including comments from Lee Felsenstein in August 2005. Subsequent comments came in 2009. This material was moved from the linked Web page which included this and the other discussions.

I've recieved permission from the correspondents to exerpt their posted correspondence. If I recieve private technical correspondence, I'll publish it here as well. I'll be glad to add links and make corrections to this document when requested. See or other archives, to access Usenet comp.os.cpm archives.

My thanks to the participants: Amardeep S Chana, Barry Watzman, Randy McLaughlin, Thomas "Todd" Fischer, Axel Berger. Thanks to Lee Felsenstein for his comments on Processor Tech; and additional work on the 16FDC done by Emil Sarlija, and discussion from Mike Stein.

If you don't know what "S-100" means (or means to me), start with my S-100 Web page. My email address is @ another page.- Herb Johnson.]

2004 comp.os.cpm discussion of Persci drives and Processor Tech

>Persci drives and Cromemco 16fdc

Amardeep S Chana:I finally got around to cleaning the heads and setting the jumpers on a dual 8" drive unit so it could be hooked up to my Z-2. The drives are Qume 842 DSDD units. As it turns out, much to my dismay, the [Cromemco] 16FDC 8" disk connector is wired for Persci disk drives and will not work properly with standard Shugart type drives without some board mods.

[See the linked Web page for further discussion about the 16FDC controller. - Herb Johnson]

[See the linked Web page for further discussion about Persci drives. - Herb Johnson]

Persci drives, Processor Tech and Helios (exerpts)

Barry Watzman: Later this summer, I will have at least one, possibly two, Processor Technology "SOL-20" and "Helios" combinations (I'm currently rebuilding a stash of Processor Technology equipment that I recently purchased). The SOLs will be (already are) tested and working, I'm not yet sure of the condition of the Helios' (Helii ??). The Helios box was just a very sexy Persci drive case & power supply. Since the Persci drive was indifferent to hard vs. soft sector, the Helios drive box can run CP/M as well as PTDOS if you use a different controller (the PT controller used for PTDOS was hard-sectored). Any controller that supported the Persci drive can be used, which is just about any Western Digital based controller at all (Tarbell, Cromemco, etc.).

Randy McLaughlin: Actually the jumpers for the Persci's included in the Helios were hugely different than the Persci's shipped by Cromemco. As memory serves the Helios version worked fine in a Cromemco but to use a "Cromemco" Persci in a Helios you had to re-jumper it. I no longer own a Persci but.. could you post the jumper settings for the Helios and maybe someone that has one of Cromemco's oak Persci's can do the same with theirs. Also as I remember Persci shipped the drives jumpered as in the Cromemco version when you bought direct. I still have my original Persci manual and a PDF of it is available on my Web site.

I only dealt with a couple of Helios systems. PT shipped the boot loader on cassette and I was never able to get the first one to boot (no help from PT either). I ended up putting a 4FDC on the first one. I had to translate RDOS to 8080 code and make my own CBIOS to support CP/M since getting CDOS to run on an 8080 was too big a job. Much later PT came out with different SOLOS ROMs to boot directly.

Thomas "Todd" Fischer: The Helios was single-density, hard sectored, and was available with either one or two Persci 270 drives. I don't believe that Lee Felsenstein ever specified or re-designed for the dual-density 277, or "quad-density" 299.

I, at an earlier time, had probably worked on more Persci's than anyone else, having them shipped to us at Fischer-Freitas in Oakland, CA from as far away as Australia. The Persci 270 was the single density, dual drive (in a single full-height form factor); the 277 was double density, and the 299 was dual drive, dual density.

It required a Persci 499 disk exercisor to align and test the drives. Scale lamps, rabbit hair head pads, voice coils, and glass positioning scales were the most common replacement parts. Persci was sold to another group in late 1980, with the result that parts became VERY expensive.

My wife Nancy and I bought out a portion of the Processor Technology inventory when they went bankrupt in 1981, primarily for the Helios/Persci inventory. The Persci had about 27 documented jumper configurations for various OEM applications. I disposed of my exerciser and documentation in 1989, so don't have any of my original notes and documentation. I still have two of the 277's available for anyone who has a keen interest. Both were working when last used, and they are jumpered for soft-sector, double density operation with the IMSAI disk controllers. This should be the same as Morrow Disk Jockey, CompuPro, and other similar controllers that used the Shugart 851-style interface.

I always related the Persci as a kind of exotic European sports car; incredibly fast for the short term, but prone to regular service and adjustment. An innovative, but unreliable and complicated design.

Randy McLaughlin:My experience is tiny compared to [Fischer's] but my experience says they are fast, I loved mine when I had one.

It was from memory that I stated that the 277 was rated for FM. After reading your post I opened my 16FDC manual (available on Howards site) and Cromemco recomended not using the 277 for MFM (page 61 of the 16FDC manual "Note that the PerSci Model 277 is not specified for for double density operation"). My Persci manual doesn't say anything about density at all. My experience with the 277 agrees with you in that I never had any problems with MFM.

I only dealt with two Helios systems, both came with 277's but the Helios controllers were FM. On one I ended up setting up the drive to work with a 4FDC. Both systems were a pain to get running. The PerSci drives worked fine........

When Cromemco came out with the 16FDC's I got one very early and was heart broken when they said I should now turn around and buy and expensive 299. I never bought a 299 for myself I used my 277 from the beginning with no problems (luckily). I talked to Cromemco and they reiterated that I shouldn't use a 277 with the 16FDC, I ignored their advice.

[See the linked Web page for further discussion about the 16FDC controller. - Herb Johnson]

[See the linked Web page for further discussion about Persci drives. - Herb Johnson]

Processor Tech's rise and demise:

Editor's notes: Processor Tech was an S-100 manufacturer in California from 1975 to about 1981. See Lee Felsenstein's later comments about its history. Here's what was discussed in this comp.os.cpm thread. - Herb

Randy McLaughlin: I loved my SOL-20 and all of their software. I hated the Helios. I never understood some things about the Helios: No boot ROM; they shipped long after the 1771 dominated, yet they went hard-sectored; [and] they went with their own DOS long after CP/M was available (Lifeboat had a CP/M available). PTDOS was interesting but to my knowledge had no real advantage over CP/M.

Other than the SOL-20 I was always fairly underwhelmed by their hardware in general. I do agree with others that a better SOL would have been nice. As I remember the SOL-20 came out before the Z80 and when everyone thought 64 by 16 was fine for video out.

Imsai did deliver "a better SOL", I made a few myself using an Imsai VIO, and a Cromemco ZPU & 4FDC inside of a TEI chassis with a built in monitor.

Thomas "Todd" Fischer: I firmly beieve that the reliability failures, coupled with the high initial cost, sunk both Processor Tech with their Helios, as well as IMSAI with the VDP 80, both being cumbersome and heavy to ship, and prohibitedly expensive to have to deal with under warranty.

Barry Watzman:I'm not sure that the Persci was what sunk PT, but I think that the Helios and PTDOS did. If PT had used CP/M with a WD based controller, it would have made all of the difference in the world. The other thing that they needed to do was a "SOL-II", with a 4 MHz Z-80, 80x24 video and the system firmware and video in high memory (F000 instead of C000). It's interesting, PT did not go bankrupt, they simply shut down while still solvent.

Randy McLaughlin:How they released their software at the end was strange. They sold copies and rights of the original sources to individuals & groups non-exclusively.

I agree that the Helios/PTDOS was one of the big killers. The buzz at the time (dealers in Houston, TX) was that the extended basic that was supposed to go with the Helios was NorthStar basic and when they didn't come up with a controller & DOS NorthStar developed their own.

They were at least a year and a half behind promised scheduled deliver of the Helios. I am not sure of the sales of the SOL-20 at the end. The Helios controller was a piece of crap.

They had a large hard drive (I believe that it was 75mb) interfaced to a SOL-20 running PTDOS but never even advertised it as something they were going to sell.

Thomas "Todd" Fischer: I beg to differ... Marsh and Ingram moved their growing operation from Berkeley to Pleasanton (the former Johnson-Pacific Volkswagen distribution building) in about 1978-79 that rented for $30,000-$35,000 per month. Add to that oppulance the cost of utilities, additional overhead, and payroll. Suddenly, you have a MAJOR nut to crack before you can turn a profit.

In all honesty, not one of Lee Felsenstein's designs were exactly "production friendly". With major warranty and customer service loads, the camel wouldn't take another straw, even WITH compensation!

My wife Nancy and I bought out a portion of the Processor Technology inventory when they went bankrupt in 1981, primarily for the Helios/Persci inventory. It was kind of sad and lonely when we left [the auction]. Just as the doors were about to be locked forever, Bob Marsh gave my wife Nancy a poster that she particularly liked that formerly adorned the wall of one of the offices. There wasn't even loose change to be found among the remainder.

Barry, in private correspondence: There is disagreement as to whether Processor Technology simply shut down while still solvent or was actually bankrupt. John Dvorak (who, like me, was active in the industry when this happened) just printed in a recent column (dealing with the concept of Microsoft simply shutting down and liquidating), and in that column he stated that PT was not bankrupt when it shut down. And that was my understanding from the time, also, and I have original contemporary (1979) published reports which state that they were solvent, although perhaps headed for insolvency, when they shut down. I know that Todd Fisher's account differs with this, so I'll just postulate that this is a somewhat open question. The fact that the assets were auctioned off does not, in and of itself, imply that they were bankrupt.

2005: Lee Felsenstein and Processor Tech

Lee Felsenstein found my Processor Tech notes on this Web page, and wrote to me in August 2005. Quoting with permission:

> Herb,
> My periodic Google search on my name turned up the
> Retrotechnology page on "Persci Floppy Drives and
> Processor Tech" in which my name is mentioned a few
> times. I'd like to make a few clarifications.
> I was never a founder or a principal of Proc Tech (as
> we called it - sometimes I would call it "Proctology"
> when I answered the phone for them). Bob Marsh talked
> me into going in with him on the rental of a garage in
> industrial Berkeley in late 1974 so we could both set
> up our fledgling electronics firms. Mine was a
> sole-proprietorship doing contract electronic designs,
> mostly for former supervisors and co-workers laid off
> from Ampex Corporation (where I had worked 1968-1971).
> Bob was looking for a product to manufacture -
> especially one which could make use of center-cut
> walnut pieces he could get from a friend who had moved
> to Wisconsin and was in the wood business. He
> considered a digital clock but his attention was soon
> drawn to the Altair in January of 1975. He convinced
> me to drive him to the first meeting of the Homebrew
> Computer Club in March. Soon Processor Technology
> Corporation was born, but I was an outsider who
> contracted to them to do design and documentation
> jobs.
> My major works for them were the VDM-1 and the Sol-20.
> Unfortunately, I was not allowed to do the PC board
> layout for the VDM-1, and it went to a totally
> inexperienced guy as his first job. It shows. I would
> hate to have to defend that piece of work, which was
> laid out without a pencil preliminary layout and has a
> ribbon cable conducting the data bus across the board
> as an admission of failure. I could have done it much
> better.
> And of course, my contract included a royalty, which
> was the best money I ever made. Not the most, but the
> least encumbered.
> Still, at one point in 1976 I was asked, entreated,
> nay required to come in and serve as acting interim
> engineering manager. Management thought that there
> were only a few tasks remaining to be done. I
> interviewed all the engineers and came back with a
> list of at least twenty major tasks. When Gary Ingram,
> the President and co-founder heard this he cringed and
> waved me away, shouting OK! OK!.
> It was at that time that the Helios design was being
> completed for manufacture. I deny any responsibility
> for that, the memory boards, or nearly anything. When
> I got free of that entanglement and the company moved
> to Pleasanton (Gary's home base) I would journey
> weeklyi down there from Berkeley to talk with them
> about new designs. Eventually I took on other
> contracts and when finally I asked them "what the hell
> do you guys want?" they replied, "we don't know, we
> were waiting to see what you came up with." During
> that time (several months in 1978) I could have done a
> lot - like a Z-80 Sol capable of CP/M, for example.
> Bob Marsh has told me that one of many stupid things
> Proc Tech did was to get adversarial with North Star
> and get into a lawsuit with them (over a disputed
> version of BASIC). He says now it's clear that they
> should have cooperated in integrating the North Star
> disc system into a new version of the Sol. Sigh.
> Proc Tech closed its doors in 1979, just before the
> National Computer Conference in New York. I know
> because I was there with my VDM-2 almost-working
> prototype looking for their booth, which never
> appeared. I have also heard stories recently that
> indicate that they closed down not out of necessity,
> but out of choice. I will not repeat those stories
> because they reflect well on nobody. It's over.
> Using the Persci disc drive was one of many small
> disasters that compounded to bring them to that point.
> I can't take responsibility for the design
> misdecisions - I had nothing to do with them. It was a
> clear case of amateur management and growth beyond the
> level which will tolerate such management.
> Of course, it's always tempting to wonder how I might
> have integrated the North Star controller onto the
> main Sol board and maybe included some of the VDM-2
> features (smooth scrolling, writeable font) in the
> design as well, using chips that were available at the
> time. That would have been a killer!
> Lee

When I asked his permission, he replied:

"Herb, Permission to reprint is granted.

"Also, you might want to note that Proc Tech's first product was a 2K EPROM board, but this is nit-picking. The 4KRA RAM board was the first significant product - one that made the Altair a workable machine for the first time. When [founder Bob Marsh] peeked into MITS' Altairs at the World Altair Convention in Albuquerque Bob Marsh said that he saw many 4KRAs in the boxes.

"I don't have a website but am getting one together. I can link [you to] it when it's ready, but the focus will not be on computer history.

Thanks for doing this. History has much to teach us. - Lee"

Herb Johnson
New Jersey, USA
To email @ me, see
see my ordering Web page.

This document copyright © 2010 Herb Johnson. Other people may exercise copyright on their authored materials as they see fit.