Digibarn Stories:

Bill Pentz and (Earliest) History of the Microcomputer

The World’s First Fully Functional Microcomputer (with peripherals)

the “SacState” or “Bill Pentz” 8008 Machine of 1972-73

(August-November, 2008)

Lee Felsenstein viewing and Bob Frankston commenting on the

Sac State 8008 early microcomputer
from Bruce Damer on Vimeo.

New: 2009 IEEE Annals of the History of Computing article on “The First Micrcocomputer?”

(also see draft version with more images)

Video interviews with Bill Pentz (by Allan Lundell)

Bill Pentz (outside barn) & the story of the Intel 8008 @ SacState Bill Pentz (inside barn) & the story of the Intel 8008 @ SacState

A rendition of the story (by Bill Pentz with some additional wording by Bruce Damer)

In August of 2008 Bill Pentz first visited the Digibarn to give us his early IMSAI computer with considerable original software and documentation. As we interviewed Bill we realized he was involved in the not well known personal computer history that we established the Digibarn to preserve and share for future generations. Bill’s version of this early history differed so strongly from established histories that we were confused. At the same time Bill was not someone to ignore as he taught university computer science engineering for over thirty years and his hardware and software donations showed he was clearly very technically knowledgeable. We asked Bill if he could share more about that early personal computer history that predated the Altair. He shared considerable information and thought he might find the early 8008 computer that he and his team used with some early medical software applications. Bill said he gave his friend John Moorhead that equipment years ago. We were very excited when Bill not only located John, but John agreed to let Bill donate that equipment to the Digibarn.

The Intel 8008 processor on Bill Pentz’ “SacState” machine, 1972

We already knew that CTS who later became DataPoint had engineered an Intel 8008 micro controller chip into a working computer in the early seventies years before Altair announced their personal computer. CTS then sold their units as “smart” video displays and key data entry stations because they did not feel they could market their product as a real computer. It had too little storage and programming space to run “real” programs plus everyone “knew” real computers took up large rooms, needed raised flooring, monster power supplies, etc. What Bill gave us shows that Tektronix, Inc. of Beaverton Oregon was doubly involved during that same era with this same early technology. The Tektronix 4023 graphics display terminal contained its own processor to do graphics plus Bill donated the parts that show with etched in 1972 and 1973 dates that Tektronix was already using fast serial interfaces, cassette tape interface, internal modem, and various memory cards that did not appear in the personal computer world until at least 1975. Additionally, Bill shared a whole host of different things that all came together between 1972 and 1975 that we believe helped move microcomputer based computing forward.

Curator Bruce Damer note: Jack Rubin’s comment/correction about Datapoint (5 Jan 2009):

Datapoint did not use an 8008 in their “smart” terminal (the Datapoint 2200); rather they developed a programmable terminal using discrete logic and then went to both Intel and TI, asking that a VLSI chip be developed incorporating their instruction set. This was to become (at Intel) the 8008, developed largely in parallel with the 4004; the TI project took a different path. Bottom line, both companies failed to deliver a chip to spec and on time. Datapoint ended up staying with discrete logic – faster at the time than the microprocessor – and passed on the 8008.

Bill shared a most amazing history! It turns out that Bill led a team at California State University, Sacramento on the COMERs (COmputerized MEdical REcords System) system. This system was commissioned by Garry Gordon, MD who was president of the American Medical Preventics Society. Dr. Gordon was one of the first physicians to recognize the significant damage that people built up from years of too much lead exposure. Dr. Gordon and his fellow physicians were also interested in a long term study of that approach to also reduce atherosclerotic plaque buildup. Sac State upper division Computer Science major Gary Johnson was charged with writing a host computer program that followed the Sacramento Medical Preventics Clinic patients over time to help prove the value of the heavy metal detoxification and assist physicians to find problems before they became acute. The cost to use the campus host computer was so high a few of the easier applications involved in this COMERS project were ported over to run on an Intel 8008 microprocessor system. We believe the result is one of the first ever complete computer systems run by a microprocessor. It all started in the spring of 1972 after Bill arrived at his new job with the new Computer Science Department within the School of Engineering at California State University at Sacramento aka “Sac State”. Bill found a couple of boxes in the secured digital parts cabinet that contained just-shipped Intel 8008 micro controller chips. These were Intel’s first step beyond their 4004 which changed the already reeling electronics world.

A bit of Background: the Post-War March to VLSI

The electronics world did a near total flip flop when the tube based technology of World War II was replaced by transistors. Firms that embraced the new transistor technology thrived while those stuck supporting and selling tube technology mostly soon went bankrupt. Why would anyone buy a tube based TV for $500 when $250 would buy a far better and more reliable transistor based unit that also displayed in pristine color? This cycle repeated itself again when the aerospace technology of the sixties replaced whole printed circuit boards with single integrated circuit chips. The time between tubes and transistors was about twenty years. The time between transistors and integrated circuits was about ten years. And the time between integrated circuits and the next major change with very large scale integrated (VLSI) circuits was bare five years.

VLSI circuits of the late sixties and early seventies created a huge bank of almost every type of digital function onto a large single chip. Unlike prior integrated circuits where the function of the integrated circuit chips was set during manufacture, how these digital electronic function were combined on some VSLI chips was controlled by an internal read only memory (ROM). Most hear the word memory and immediately think a ROM is something that stores computer information. Although a ROM can do this, how a ROM works is more like having all prewired with fuses that will let an electrical engineer break all unneeded connections. We call this ROM burning because we actually burn out the unneeded connections. There are so many connections involved with a VLSI circuit that electrical engineers used a computer program to oversee burning away the unneeded connections. That is why setting up a ROM became known as ROM programming. For VLSI circuits where the ROM was part of the chip, this internal rewiring using a programmable ROM (PROM) programmer became known as firmware programming. Just like building a dedicated circuit the result left a single function hard wired circuit. Because VSLI chips were expensive, a number of organizations built specialized computer programs that let them test their “firmware” before they actually burned their VSLI circuits.

As VLSI circuits became ever more complex many added random access memory (RAM) to the internal VLSI ROM memory. This RAM allows a circuit to change its function based on the value in each internal memory location. Testing these variable circuits caused considerable grief. The MicroData minicomputer corporation built a very powerful general purpose minicomputer system that used electrically erasable programmable read only memory (EEPROMs) that let that computer be programmed with the firmware to create just about any kind of VLSI or computer circuit. Bill Pentz was the firmware expert for Sac State and he wrote an advanced firmware test program that permitted testing these complex circuits before they were burned. It turned out that system also provided a quick way to find problems in existing circuits, so soon Sac State was involved in many different VLSI computer and complex circuit implementations. IBM gave Sac State a nice grant in trade for turning their very popular IBM System 3 into a viable design that could be made with existing VLSI microprocessor technology and only 4k of ROM. That work earned Bill a weird reputation as the guru Sac State kept locked in a tiny little room that they fed coffee and raw meat. Bill insisted the raw meat rumor was not true but he did like coffee, lox, bagels and cream cheese. Although Sac State gave away that software, many early minicomputer firms that transitioned to using VLSI technology called upon Bill to help with debugging their projects. Bill also helped with the DEC PDP 10, Varian minicomputers, and helped model other systems. In fact, in Tracy Kidders’ book “Soul of a New Machine”, Bill was one of if not the university guru that Data General went to for help when their microprocessor design stumbled. The bottom line is that with the right software support a company in a few days got more done than they used to be able to do in years of work, plus could replace a good portion of the need to make specialized boards. In fact VLSI cards with standard interfaces rapidly replaced many specialty circuit boards.

It all Started with a Bet

Bill, on a bet with a faculty member, used a DigiDesigner prototyping board to turn one of the Intel 8008 VLSI general purpose controller chips into a simple but working computer in mid 1972. Unfortunately, the result was so fast that none of the Sac State analog or digital test equipment could track the signals to determine why this plug in wire wrapped system would not work reliably. Frustrated with that poor reliability, Bill got help. Russell Light, the Sac State head electrical engineering technician designed a more stable circuit. Dave Mack, the other Sac State electrical engineering technician turned that circuit into a working printed circuit board. This made a much more stable computer, but the result was still useless for any real work. It still had irritating but minor reliability problems that were eventually found to be power supply problems, but the big issues were it took at least ten times longer to program to do any practical work and lacked enough storage to run more than very simple programs.

Tektronix to the Rescue!

Bill got a big break on the reliability and storage problems. He explained the 8008 reliability problem to Steven Heitmann, who was a friend from college who worked as a scientist for Tektronix Inc. in Beaverton Oregon. Steve wanted Bill to work for Tektronix, so Bill visited and interviewed with Tektronix. While there Steve showed off the incredible Tektronix manufacturing ability. Tektronix designed, built, and gave Bill a full 8008 system with control panel. This unit gave Bill his reliable “dream machine” that worked with the Tektronix 4032 graphics terminal. It also gave Bill quite a bit of memory in the form of 4023 memory ROM/RAM expansion cards. That 4023 was not only one of the best ASCII terminals, but also had its own intelligence allowing it to show graphics way before its time. With the help of the Tektronix 4023 expansion boards that system also doubled as a digital development workstation which had buss based logic probes on every line five years before the first simple logic probes were sold.

This Tektronix system created a stable platform and was an amazing machine which may well have been the “first full microcomputer” able to talk to a hard drive. The Tektronix display that held this system could then be expanded with a cassette interface, Teletype interface, paper tape interface, printer, and a modem for serial communication with a Cyber host at up to a whopping 9600 BAUD (unfortunately the Sac State host computer could only put out 110 BAUD)! These Tektronix terminals soon got color graphics at least five years before the first personal computers supported color or graphics. Although this was an impressive hardware collection it still was not that practical because it took graduate computer engineering skills to program and took at least ten times longer to program than existing host and mini computers. Also, the very expensive memory and limited Intel 8008 memory maximum precluded all but very short programs.

Bill’s Team Gets Down to Programming the 8008

Fortunately, Bill had an available fairly easy solution to solve the programming time overhead. Each different type of computer uses a different set of machine code instructions. Machine code instructions are the binary instructions stored in RAM that define what electrical logical functions a central processing unit (CPU) follows when a computer program is run. Assembly languages create one binary instruction for every human readable assembly language instruction. Because IBM dominated the computer market all Sac State computer science students had to learn BAL (Basic Assembly Language) used on the IBM System/360, 370 and later mainframes. Students had to prove their mastery of BAL by writing a working assembler, BASIC interpreter, simple compiler, operating system and data base. To stop cheating completed student program listings, card decks and outputs were collected and stored in a locked area that faculty members reviewed to ensure students did not copy prior programs. Bill recognized that all he needed was for the Intel 8008 to run the same BAL instructions. Bill had just finished a large graduate student project that created the firmware to make an IBM System 3 minicomputer run on a 4K based VLSI based computer. Bill simply changed that code so BAL also ran on the Intel 8008. This ability to run BAL let Bill’s team pick and choose between the best student programs. They soon had the Sac State 8008 running DOS (Disk Operating System) which allowed loading and starting programs stored on paper tape, cassette tape, cartridge tape, and even their mobile pluggable 3/2 (three megabytes fixed, two removable) hard disk system. They had it running a simple BASIC interpreter. Because the BAL firmware ran so slow, Bill’s team also built a BAL assembler which instead of putting out one machine code instruction per human readable instruction put out all the code needed to run in 8008 machine code.

The Little Microprocessor that (almost) Could, Was Made to Do a Lot!

See Ryan Norkus’ 3D graphic reconstruction
of how the “Sac State 8008” might have looked with all its peripherals

Unfortunately, the 8008 still just did not have enough memory to run very large programs (8K addressable which in Bill’s implementation they created two memory banks, one protected, one writeable). Regardless, this system still permitted using the Tektronix graphics screen, communications devices (aforementioned modem), paper tape and cassette interfaces, a printer (a Teletype model 40, which was a 300 line per minute printer versus our eight to ten character per second Teletype ASR-33), and use a minicomputer standard interface to also read and write to hard disc storage. It should be noted here that no microcomputer system achieved this type of integration with peripherals and a built in assembler plus operating system until well after the hobbyist movement got going in 1975. It was not until closer to 1978 that microcomputer operating systems actually provided this same level of standardized I/O and more than just the ability to load and run programs. The speed of the 1973 Tektronix 9600 baud serial communications interface was unheard of before about 1980 when high density floppy disks and higher speed modems came on the horizon. It should also be noted that the famed Altair 8800, Homebrew Computer Club and Apple Computer were still years in the future when the Sac State machine was up and running with all of these features.

The complete set of boards from the Bill Pentz SacState machine (on display at the Digibarn) It is thanks to John Moorhead preserving this equipment that this complete set of boards from the Bill Pentz Sac State machine is now on display at the Digibarn.

Running BAL and having hard disc drive access transformed the 8008 microprocessor from a problematic and limited device (it had serious timing problems) into a limited but working computer. The host computer costs for the COMERS medical project were so high, that Bill and his team ported over some of the simpler applications and started running them on that 8008 system in late 1973. Eventually that system was running a nutritional analysis, medical history, genetic history, and graphical output program to take advantage of the Tektronix 4023 color graphics. This system also replaced the need to work with 80 column punched cards for entering data onto the mainframe. Bill’s background in writing firmware now known as microcode was an essential ingredient to the success of this project. CSUS shared most of what Bill and his team had done with Intel in hopes of trading future help for more equipment and support.

Intel asks Bill for Help on the 8080

In 1973, as Intel was developing the 8080, successor to the 8008, Bill was asked by them how they could improve the 8080 based on his experience working with the 8008. His initial response “bundle our BAL/DOS system with it and you will have a real computer” or “add more addressing modes and instructions, and here they are”. Intel balked at including the 1702 PROM-based BAL as these chips were famously expensive, the results ran terribly slowly and IBM owned that proprietary language. Intel did take Bill’s advice on the instructions. Meanwhile these primitive VLSI general purpose controller chips finally got named microprocessors. This made sense because they had all of the main features of the simple processors found at the heart of mainframe computer central processing units, but were microscopic in size and were minimal functioned.

Enter Gary Kildall

About this time Intel went out looking for a consultant who would take the CSUS work and take their pretty box and come up with their own unique programming language to turn the new 8080 into a fully functioned computer that could compete with the low end minicomputer systems. A young consultant/software engineer named Gary Kildall was hanging around Intel and considering taking a contract with them to help productize such a complete commercial microprocessor based minicomputer system. He was given copies of all the 8008 and 8080 work done by Sac State as background for this possible project. Gary opted not to take the contract and instead went on to write CP/M (Control Program for Microcomputer) and form his company Digital Research and the rest is history.

Curator Bruce Damer: I have include a note of clarification regarding Gary Kildall’s role, sent by Herb Johnson (5 January 2009):

Dr. Gary Kildall, professor of computer science at the Naval Postgraduate School, wrote Intel’s cross assemblers and compilers for the 8008 and 8080. These products were sold by Intel and widely used on minicomputers and mainframes at the time, as they were written in portable FORTRAN. Kildall developed one of the first high-level languages to be used on microprocessors, namely PL/M – again, a product sold by Intel. Kildall himself wrote articles in computing and engineering journals on these products and their use. Numerous sources including Kildall’s own accounts, all cited on my Web site, will confirm these statements.

Of course, Kildall also developed CP/M in the 1973-75 timeframe. It was based on his prior 8080 and 8008 work, and his desire to expand PL/M to support a file system on a floppy drive. Kildall was primarily interested in the use of high-level languages on microprocessors. Almost all of this is documented by articles in the literature of the time.

Kildall himself accounts that he offered his CP/M system to Intel, who then turned it down. Kildall was eventually convinced by his colleagues to offer CP/M as a product, early in 1975. Meanwhile, Intel developed their own diskette operating system for their Intellec 8080 called ISIS, primarily as a development environment and not as an embedded operating system. The development history of ISIS is not known to me. But I’ve documented, on my Web site, a number of early operating system commercial products for floppy-based microprocessors. Consequently, I’d be interested in more information about the Pentz work, including references to any articles published about it at the time or later. It would be informative to add that system to the ones I’ve discussed on this my web site at: http://www.retrotechnology.com/dri/index.html

How History Could Have been Changed (by Bruce Damer)

It should also be noted that if Intel had taken Bill’s advice and marketed a commercial microcomputer with BAL/DOS from Sac State it is quite likely that today we might not have a Microsoft (not such a big need to create BASIC on paper tape when you have a real assembler and OS already in ROM) or even an Apple (Steve Wozniak could have just used a “Sac State machine” to write all the color games he wanted, no need to form a company with Steve Jobs when the machine already did everything you wanted).

One thing that occurs to me is that in 1975 the Homebrew Club members got their hot little hands on 8080 microprocessors all ready and working for their microcomputer kit projects but never asked “hey, who debugged this, who turned the not-so-functional-beta-versions of this into the well-its-ready-to-build-stuff-with 8080?”. There is always a story behind the story. Of course, like everything else, the 8080 did not emerge pure and functional “from the void”. For this computer collector and curator the story of Bill Pentz and the Sac State Machine has been one of the most satisfying projects ever here at the Digibarn.

News Spreads of the Sac State 8008

The user’s manual from the Intel 8008 MCS-8 Microcomputer Kit (November 1973) see local copy here

The 8008 was packaged as a kit and offered by Intel in November of 1973. The cover of the MCS-8 manual shown above pictures the box designed by Sac State and contains much of the experience of the Sac State team gained while working with that early 8008.

Curator Bruce Damer note: Jack Rubin’s comment/correction about the MCS-8 (5 Jan 2009):

The MCS-8 was not a computer kit but a fully built development system, designed to aid engineers in learning about and developing 8008 systems. A full system included software (on paper tape; a paper tape reader was an accessory for the system) to edit and assemble 8008 code and then burn the code to PROM. Just stuff off the top of my head and far from authoritative. More later. The Datapoint story in particular is really fascinating and deserves better coverage. CHM has a fantastic series of interviews with many key Datapoint people but I haven’t been able to get access to all of them.

When Popular Electronics announced a working Sac State designed microprocessor based computer (we are trying to find that news item, it is not in the July-December 1974 Poptronics, anyone have other issues to check?), that still infant department was deluged with phone calls, many from HAM radio enthusiasts, trying to make the 8008 do something. Word had gotten around about what the Sac State machine could do but the cost of parts and degree of programming difficulty precluded most from pursuing this early technology. Only the fortuitous sharing of programming expertise and hardware resources shared between Sac State and Tektronix made that early working system possible. As mentioned above, also in 1973 Intel was developing the 8080 microprocessor and Bill’s team received theirs in about December of that year. They quickly moved on to build another, much more comprehensive microcomputer setup to move more of their large medical application of the expensive host computer.

Stan Mazor’s input

Bill Pentz explaining the 8008 project to Stan Mazor, the co-inventor of the Intel 4004 microprocessor (DigiBarn visit on Sept 27, 2008)

Curator Bruce Damer’s note: Stan Mazor sent in the following first person impression on December 31, 2008:

Personally I’ve written 4+ articles on the the chip history at Intel, and have briefly mentioned Intel/my involvement with Datapoint/Computer Terminals. Gary Kildall’s history has been covered in a number of places, and mis-represented in the video about the ‘computer nerds’, in my opionion, as that video contradicts what’s generally written about it. We’ve covered that story very well in the past. Pitman created a small portable ‘pc’ using the MCS-4, and there were numerous computers built with the 8008. My general problem is that the only obvious use of a CPU is to build a computer, so it’s hard for me to see what is enlightening on that subject, generally. I started programming in 1961, and had programmed more than 6+ different computers by the time I worked on the 8008 in 1969. Also I had designed more than 3 computers by the time I was working on the 8008. (For example Fairchild Symbol was a pretty interesting machine.)

Bill’s career after the 8008

Bill also was involved in many other activities which eventually impacted the personal computer revolution. Later, Bill ended up being a facilitator who helped put the various people together to come up with the IMSAI 8080 to create a better design than the early Altair. One of Bill’s friends, Dallas Parcher a digital electronics technician for AT&T’s first digital switching network went on to repair the many early design and timing problems that plagued the early Altair and IMSAI 8080 personal computers. Bill meanwhile was earning his living as a professional host computer programmer and analyst. He designed and oversaw the development team who created a computer program that helped balance government budgets. When faced with the need to hand in a perfect departmental budget with no erasures or white out changes he designed and wrote a subvention system that became known as the Governor’s Budget Estimate System. That system used row numbers and column letters to identify unique cells. Every cell was composed of a value, character string, or formula. His system ran each set of values twice as it had to create an intermediate COBOL program to figure out the formulas. This system also allowed the user to setup automatic subtotaling based upon indentation of items in the first column. He later changed this system to use the Waterloo BASIC which allowed using IBM color terminals to make changes on the fly and instantly recalculate. This package was widely distributed by IBM under the names Budget Estimating system and MainCalc, a mainframe-based accounting application. It may well have been the first spread sheet that inspired VisiCalc (we don’t know just yet) and much more.

– Bruce Damer, Curator (with thanks to Bill Pentz for numerous corrections and additions)

View Bill’s interview by Allan Lundell and see photos of the visit below. We could also use your help to fill out this story more, see our Call for Help below.

More from Bill Pentz

Bill’s emails on his roles, history and the provenance of the donated artifacts (more writing from Bill to come):

Bill’s email of Nov 14, 2008

Bill on reading the 1702 PROM chips for the original 8008 DOS and BAL implementation

I don’t think you will be able to get much from those 1702 PROM chips even if you can read them. What I gave you are the pieces that Tektronix gave me directly, but the actual working 8008 based system was a combination of the parts I got plus the parts that CSU Sacramento got in trade for helping to program the 4023 Tektronix graphics terminal software. My first 8080 used that same Tektronix 4023 test bed and the same PROM/RAM boards that we upgraded the software to work with the 8080 instruction set. When we left that Tektronix motherboard system in favor of what became the S-100 standards, I copied the Tektronix design and cannibalized the 2102s RAM memory chips and 1702 PROM chips from my 8008. When I upgraded our 8080 to use 2708 PROMs the school owned 1702/2102 PROM/RAM boards went to our electronics shop where they removed the pieces and put them back in stock. Anyhow, when all is said and done, I am near certain that what is on those PROM chips is software for driving the 4023 Tektronix terminal. I think the PROM/RAM boards I gave you were additional 4023 terminal spares I talked Tektronix into donating after they had upgraded.


I know you would like to have a copy of that early DOS and probably the assembler, BASIC interpreter, and BASIC compiler we used. I have gone through all of what I have left and I don’t even have a software listing or paper tape to give you. I checked with CSUS just in case some of that stuff got tucked away in a corner. The fellow who took over from me still works there at CSUS, but has long been a part time lecturer. He kind of laughed when I told him what I was looking for. It turns out that in one of my other roles I managed to get CSUS an IBM 360 donated with free IBM maintenance. That machine ended up taking over my old lab and the adjacent class room. They did a clean sweep of all the projects, software archives, and hardware that was laying around when that host system came in.

On the SacState Machine’s Disk Operating System (DOS)

Anyhow, in the early seventies software engineers provided the basic minimum programs that came with each computer, meaning a simple operating system, assembler, compiler, and interpreter. Programmers then wrote programs using the vendor supplied software. One of the first exceptions was Waterloo BASIC which got sold for a small copying and handling charge. For us to get a good DOS was basically a dime a dozen proposition as I had a cabinet of what our students had built over the prior two years. All that we really had to do to make one of those work is insert the same disc drivers from our Microdata Minicomputer that shared that same hard drive into the DOS jump table. All of the rest was simply matching ports, status bits and in a few cases interrupts to make that single task operating system work. If I could find a copy, what you would see is CP/M is an exact duplicate of what we built except the disc drivers were converted to work with a floppy disk instead of a hard disc. The floppy drivers were more difficult to write because the hard disc drives had their own standard logic, simple timing, and simple handshaking. I was calling that standard interface SCSI back in the early seventies, but one of your guests when I was there for that reunion said SCSI was a Shugart invention of the early eighties. Upon further recollection those may have been the Memorex and Centronix standard interfaces. Regardless, almost all of the minicomputer vendors then bought their peripherals from the same vendors, so almost all used the same interface standards.


On MainCalc


View of MainCalc Listing (early 1980s)

MainCalc was previously known as the State of California, Department of Health Services Accounting Claims System. I then rewrote it in I think 1974 to be even more general purpose for the State of California, Department of Social Services Subvention Budget Estimate Tables. The Subvention System as that package became known allowed more user flexibility again using a row number and column letter to define each cell location. It likewise allowed each cell to be a formula, value or ASCII character string. It also reserved the A column for defining automatic subtotals based upon the amount of indentation of each row name. It then became even more general purpose when I called it MainCalc that let us use the early IBM color terminals to interactively input the cell contents and get immediate results. I know IBM put both the Subvention and MainCalc versions in their libraries as I got requests from all over to add enhancements and additional features. Instead I ended up getting booted kicking and screaming into management for the next twenty years of my career.

From Bruce Damer, curator: I am trying to get in touch with Bob Frankston to see if MainCalc was know to them at Harvard when they were writing Visicalc in 1979.

Other Artifacts Bill donated to the Digibarn

This includes a 8080/Z80 system with dual 8 drives, printer, Diablo typewriter/printer, EPROM eraser, and much of the early software used to create such things as DMON OS (Dallas Parcher) that predated and along with the CSUS TOS was used to create CP/M, the VMON editor which was copied along with the Don Tarbell code to create Electric Pencil, MainCalc which was used as a pattern to create Visicalc and Supercalc, WordMaster which became WordStar, the CSUS (Aaron Mitchell then graduate student and now IBM software engineer) BASIC which Paul Allen and Bill Gates used to create Microsoft BASIC, plus the code and papers that pretty much helped start much of the PC revolution. Although there is a small group in the Monterey area who would like to claim they invented everything, the reality is it was a very few of us who worked tightly together freely sharing to create the PC revolution.

PC Evolution – by Bill Pentz

Although I would love to say that my early contributions to personal computer evolution or perhaps revolution resulted from careful planning and diligent work, the reality is I was nearly killed on an Air Force Reserve flight after taking in too much rat and flea poison. After three days in a coma my doctors said I was dead but too stubborn to die. I pulled my IV and fled to Sacramento to Dr. Gordon’s Sacramento Medical Preventics Clinic where I immediately started their detoxification programs for both heavy metal and organic poisons. Even with that help the prognosis was grim where my survival was a day to day issue. My doctors warned me they did not expect me to live through my next cold or bout of flu. I decided to leave a legacy before I checked out moving our Sac State medical project onto an Intel 8080 microprocessor based computer to prove that technology and try to help physicians so they could better track their patients.

As the Sac State computer technician that built software and tested many different minicomputer and VLSI systems, I had source code for most minicomputer operating systems, assemblers, compilers, and even the application code for word processors and key data entry stations. I hid as the computer technician for CSUS was working day and night to steal pieces software ample to turn “our” 8080” into a viable computer and permit it to run our medical software. One of our faculty members saw what I was doing and suddenly I had unlimited access to the computers and hardware at CSUS, plus had lots of help and contacts from other colleges. I also traded shamelessly on all the help I had given Intel, the different minicomputer firms, and others with VLSI projects. I managed to beg or perhaps extort would be a better word enough memory chips to have a full 64K machine by late 1974. With memory then costing about $100 per K (thousand bytes), our 64k machine contained over $100,000 in today’s dollars in just memory. The good news for at least me is that project kept me going through a rough time, I mostly recovered with about half the IQ I had before, and the resulting system received nice awards and praise from the American Medical Association, the California Medical Association, and the Food and Drug Administration. Additionally, almost all of the software I shoved together got released into the public domain and helped launch all kinds of new things.


Anyhow, just to bust a couple of the many myths, Paul Allen called me complaining that the version of BASIC he got from the San Diego Microcomputer Users Group which was part of that COMERS project had an integer math problem and he wanted me to make repair right then. He apparently got a copy of a copy of one of our earlier versions that was written before we figured out we had to follow Robertson’s second method for twos complement integer arithmetic. John Katowski (spelling?) was my counterpart at the UCD Physics department who designed all kinds of early microprocessor hardware and prototypes. He built for me a very compact 8080 based computer that fit in the same case as my monitor creating one of the first portable personal computers. John and I went to one of the early microcomputer shows in San Francisco. Steve Jobs was sitting on a wooden peach crate telling all his design in another box of wires that did not work was the computer of the future. He said that mass of wires was not working because something was bumped getting that mess to the show. John, who later became an IBM hardware design engineer, took pity on Steve and designed the Apple II system board which was the first version that actually worked no matter what is claimed today.


~ Bill Pentz

Photos of Bill Pentz’s Visit

Where we could use your help!

Do you have any insight or background during this period either with SacState, Intel, Tektronix or in general, that could help shed some light on this story? Do you have a Tektronix 4023 or Memorex disk drive system you could donate for us to be able to put back together a semblance of the more complete pieces of the SacState 8008 system? Do you have any Popular Science magazines from 1973-74 you could donate or look through to see if you can find the little news bar item (Bill thinks it was in yellow) that talks about the SacState project with the 8008?

Other Resources Related to the “SacState” Machine

Tektronix 4023 Manual, found locally here (7MB PDF) and on Bitsavers here.

Memorex 630 drive, possibly the one used by the SacState 8008 Machine (source Computer History Museum archives: sheet 22 of Memorex brochure)…

or was it the…

Diablo Model 33/30PB (see PDF brochure here)? This is the 2315 cartridge also used on the Xerox Alto.

Wikipedia’s Pages on the Intel 8008 and Gary Kildall

The MCS-8 User Manual (PDF) with 8008 Data Sheet at Classiccmp (local copy here)

Herb Johnson’s site The first floppy controller for CP/M and S-100?

Dan Bricklin’s VisiCalc page

Our pages on the Homebrew Computer Club

Our Altair 8800 computers

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