Email interview with PSpice founder Paul Tuinenga

From LTwiki-Wiki for LTspice

To Paul Tuinenga, on Fri, Aug 2, 2013 at 10:33 AM, <analogspiceman> wrote:

Hello Paul,

I am currently writing a bullet point history of the popularization of SPICE in the engineering community. The emphasis is on the path SPICE has taken to arrive on the most engineering desktops. Because of this emphasis, my history begins with the original Berkeley SPICE variants, continues onto PSpice (its limited, but free student version made SPICE ubiquitous) and culminates with LTspice (because, at over three million downloads, it has reached many more users than all other SPICE variants combined).

I am lacking solid information about the beginnings of PSpice, but I understand that you may have been one of the founders of MicroSim and was hoping you might be able and willing to help me to complete the section about PSpice. Please see:

Specifically, I really have no idea who were the people initially responsible for creating PSpice. Also, I could not find any information as to when and at what revision Probe became a part of PSpice. (Perhaps at the initial release?)

Then there is the meaning of name itself. I vaguely recall that PSpice was at some point called uPspice (the 'u' being a micro symbol), thus the acronym may have stood for micro-Processor SPICE (others suggest it meant "Personal SPICE" or "Personal-computer SPICE").

Last of all, I would like to list the timing of the introduction of the most important and innovative features of PSpice (a very weak start at this is up on the LTwiki).

I hope I have the facts straight and would be happy to take an suggestions for corrections that you might have (if you are so inclined). The wiki is a work in progress and any useful feedback and helpful information provided regarding PSpice would be greatly appreciated.

Best Regards

On Fri, 2 Aug 2013 at 7:40 PM, Paul Tuinenga wrote:

I will be delighted to help [... jump to historical recounting ...]

PSpice was launched in Jan 1984, with a short paragraph in Electronics (McGraw Hill) magazine. I have a photocopy of that announcement, but it's 700 miles away from me just now.

"P" stands for Personal, as in Personal Computer (PC). MicroSim (an invented name... having first checked the advertising list in Byte magazine) stands for simulation on microprocessors. As it turns out, the main product idea of the company was a mistake. Between the summer of 1984 and the spring of 1985, we built an accelerator based on multiple Intel 8086s (with 8087 floating-point coprocessors), two complete computers per Multibus board, and systems with up to 12 boards. The external box attached to an IBM-PC/AT and provided over 2x the speed of a DEC VAX-11/780 minicomputer (which many companies were using 24x7 to run UCB SPICE). It was called PSpice Turbine. We sold one a week after debuting it at an EDN industrial conference. Then the industry went into a capital-spending slump and we didn't sell another for the rest of that year. In the meantime, PSpice the "shrink wrap" software, the sales of which were to "keep us in baloney sandwiches" until the real product, the Turbine hardware accelerator, took off. It never did, but every month the sales of PSpice grew. So we shelved the hardware development to re-focus on the software e.g. re-writing it from Fortran into C (then C++ much later).

Is this the level of detail you are looking for?

Best regards,

- paul

On Sat, Aug 3, 2013 at 12:31 PM, <analogspiceman> wrote:

Hi Paul,

Thank you for your response. [... cut to further historical query ...]

Some additional questions: When did you first begin working on what was to become MicroSim/PSpice (and when was MicroSim first officially launched - 1983)? Also, were you the sole (major) founder or did you have other equal partners?

Here is what I have about you and MicroSim/PSpice (btw, what is your preferred capitalization format for PSPICE, PSpice, Pspice)?

First the wiki page introduction, then the section just about MicroSim PSpice: [cut most of quote of LTwiki page]

[...] If as its primary original author, Larry Nagel is deservedly considered "The Father of SPICE" then as its essential enabler, advocate and general all-round visionary for open source electronic simulation software, Don Pederson most certainly is SPICE’s godfather. [...]

On Sat, Aug 3, 2013 at 3:30 PM, Paul Tuinenga wrote:

Yes, I scanned the LT page but purposely ignored it for my response to let you glean what you find notable.

What's just caught my eye is the verbiage around Dr. Don Pederson. If you don't have access, I'll find a copy of the IEEE Spectrum cover article on him. He is both the reason for never creating a circuit simulator as well as the reason SPICE got created.

PSpice is double caps.

The creator of PSpice is Wolfram Blume (BS75 Caltech). He sat in the office next to mine at Silicon Systems, Inc. (SSi), In 1983, SSi bought several IBM-PC/XTs. Blume was the in-house maintainer of UCB SPICE on the Prime minicomputers used for IC design and layout at that time. SSi developed most of the tools it needed (and we all take for granted today) because none existed at the time. For example, SSi was the first to make color plots of IC layouts, and using stipple patterns for the layers (these overlap in a visually pleasing way). We also created a layout-versus-schematic (LVS) that predates by several years anything from the ECAD vendors.

Knowing the innards of SPICE, and where the time was spent for transient simulations, Blume got the idea to see how fast the IBM-PC was. He tested the speed of MOS level -2 code using the Microsoft Fortran compiler. As is turns out, that test gave an optimistic result for Intel processors to accelerate simulations and thus propelled the idea of MicroSim.

The problem with SPICE being shoehorned into the PC (640KB max memory) is SPICE2 was five(?) overlays and no IBM-PC Fortran compiler had overlay capability. Blume figured out how to replace those as two programs run in sequence, with the first doing read-in and checking, then leaving a data structure in memory for the analyses to operate on in the second program. This is why MicroSim PSpice had no competition for about two years, until later IBM-PC Fortran compilers handled overlaying.

SSi was officially upset with Wolfram and "Blume Engineering" selling PSpice for $495, and demanded royalties. Blume quit SSi. Shortly after, he and I met to discuss his situation. He described this idea for building a hardware accelerator. He's not a hardware guy, but I am and I knew exactly how to build it. So I quit SSi, too, and we formed MicroSim in June 1984. Blume was the major partner.

Later, when the Turbine fizzled, I turned to software and rewrote all the device equations into C. Then I created the Parts option and built up the several thousand standard components library. Also, I wrote "the book" which eventually went to three editions (additional material in each), was translated to Japanese and French, and sold well over 100,000 copies. That last sounds small, but for technical books, which normally sell in the mid 4-figure volume range, I am Steven King. OK, I wrote a pretty good book, but Prentice Hall gets all the credit for pushing it far and wide. Dr. Richard Newton told me he saw a copy in a Moscow university office (long before the Soviet empire fell).

What else?

- paul

On Sat, Aug 3, 2013 at 3:33 PM, Paul Tuinenga wrote:

BTW, initially I was "Vice President" then later "Executive Vice President" and CFO. Blume was always President (and CEO). - paul

On Sat, Aug 3, 2013 at 1:11 PM, Paul Tuinenga wrote:  [Don't know why the time of this email is out of sequence. -- a.s.]

Correction: the minicomputers at SSi were Perkin-Elmer not Prime. - paul

On Sat, Aug 3, 2013 at 6:51 PM, <analogspiceman> wrote:

Hi Paul,

Perhaps a couple more questions if you are willing to indulge my persistence.

Was Probe available from the very beginning along with PSpice or was there a period where the only output was ASCII graphics (which went to the printer or monitor or either)? When was a pixel graphics Probe first released?

How did the student version of PSpice come about? It seems to me that getting universities to switch to PSpice versus running mainframe jobs was a stroke of marketing genius. All those newly minted engineers would come off the academic assembly line with a preexisting predilection for PSpice. Was this the plan?

[ ...regarding Paul Tuinenga's remark about Don Pederson... ]:

I assume that you referring to his influence to go "open source" as having enabled a flood of SPICE vendors to just take the Berkeley code and wrap it engineering eye candy, thereby more-or-less killing the already marginal economic incentive for commercializing the very expensive ongoing support and development of SPICE in what is a rather meager specialty niche market. Mike Engelhardt of LTC has commented that there is no way he could have spent the last two decades refining LTspice if it had had to have supported itself independently through sales profits. He already was making the basic tool for internal consumption at LTC and just tweaked it in order to give it a parallel life as a marketing lever for their rather large number of rather functionally complicated power control ICs. LTspice allows the engineering zombies [ugh, u-hhg, brains... I need brains...] to access built-in design smarts for every part in LTC's product line.


I think [...] your historical recounting should be preserved and would be fascinating, at least to a certain significant portion of the engineering community. So many engineers cut their simulation teeth on PSpice, although it seems that role has now pass over to LTspice. If you don't mind I will collect together the historical sections from you emails and create a page for them on our LTwiki.

On Mon, Aug 5, 2013 at 11:13 AM, Paul Tuinenga wrote:

I don't mind these questions, just surprised anyone is interested in ancient, narrow history.

Blume developed Probe mostly during the time I was designing and building the engineering version of the Turbine accelerator, which was convenient since he had nothing to develop code on until I got that working. Probe was available later in 1984 or the beginning of 1985, I forget but can look that up when I get back [...]

In my opinion, if PSpice was "good" then Probe was "great" in that it made the purchasing decision a "no brainer" for most. So no only was the simulation under the control of the user (e.g. no waiting for a batch queue; sure, maybe the mainframe sim took only 30 seconds however you had to wait in line for 2 hours to have it run), but viewing the results was interactive and high quality. I have always thought Probe was, for most customers, the real product. Certainly, PSpice was leading edge and convenient but it has a boring status screen, and just sits there working. Probe was an oscilloscope -- the visible face of PSpice and MicroSim. The early version supported CGA, VGA, and SVGA graphics, as I recall. A few times a week, we would field a call for a customer ordering PSpice/Probe and asking for opinions of computer and display to purchase -- they did not have a PC, yet, and were already buying PSpice as the app they were getting the PC to run!

Also, being first, Blume had complete freedom to make a clean user-interface. Everybody after had to purposely not-copy Probe.

The demo version of PSpice was available nearly from the start, and its limited circuit size was a delicate balance: showing it "had the goods" but not enough to get real work done. About once a month someone would call to see if we would increase it by "one more transistor". As if...

Recasting the demo software as a "student version" came about in late '85 or early '86 (as I recall, but I can check that later) when we found there was a mailing list of college "electrical engineering" professors available for purchase. We thought it would be perhaps a few thousand names/addresses but it turned out to be over 20,000 (as I remember and that was just domestic). To make the disc, label it, and mail it with a cover letter, for that volume, was a "break the bank" expense for MicroSim at the time. But we forged ahead realizing that if it was a good idea for say 2,000 names it was an even better idea for 20,000.

Genius? In retrospect, but that's always the way. We were confident it would be tried by a large percentage of professors or they would give to to someone to try (i.e. not throw it away). We knew it would give students with access to PCs something to play with and enhance their lab-bench efforts. And there was not much else useful to run on PCs back then ("Lotus 123", etc.), but engineering departments had invested in PCs as "the future" even without a plan for software that supported their course offerings. We were in the right place at the right time.

If anything, this knitted PSpice into the fabric of EE education. A few years later, we read in an industry rag (ED, or EDN, etc.) an article about circuit simulation that alluded to "...PSpice and all the other PSpices..." Then we knew we had made it -- PSpice had either replaced Berkeley SPICE, in mind share, or perhaps many people had never heard of Berkeley SPICE and assumed PSpice was the original thing.

We often could track the career of many customers. They would take a new job, or new consulting client, and order PSpice again. "Oh, it seems Joe is working at Floobydust Systems now." Some did it a half-dozen times.

Another competitive barrier-to-entry we erected was having a growing library of standard parts, e.g. 1N4001, 2N2222, uA709,... Immediately after Microsoft's Fortran compiler started supporting overlays there was a flood of alphabet-soup-SPICE-on-the-PC products. Not only did we make a library, but pushed it to over 1,000 components. A nice round number, and enough that even if a particular part was missing a suitable substitute could likely be in that library. And we released the Parts option, the software we used to make the library, so customers could make anything missing from the library. That broaden the market to board-level engineers without a clue as to Gummel-Poon, Shichman-Hodges, etc. models. It took the "IC" out of SPICE.

In the process of that, we upended the market for SPICE models for hire and fostered the expectation that models be unencrypted ("open"). I recall a printed interview with one of the Hailey brothers (the "H" in H-SPICE) bemoaning how Parts had ruined their $6,000/piece modelling business. Boo hoo.

Anything else?

- paul