EO 440

June 22, 2020

From time to time I am baffled that I own a computer that I do not have a blog entry about. Either I had at the time of purchase too much going on and forgot or I felt at the time that there was already enough information available in the Internet. However, as I did quite some research on some adjacent areas (which I reported on in this blog), I feel I should do the honors for this model. Meet the EO 440, a pen-based tablet computer with an usual CPU.

Wbvanrij at English Wikipedia / Public domain

According to some sources, the 440’s (and its bigger brother, the 880’s) claim to fame is that PC Magazine called it in 2012 the the first true phablet. But that’s, of course, not the real story here. The point of the EO 440 is that it should have been the first pen-based tablet with a dedicated operating system. It should have been (but wasn’t) because it was conceived (and nearly built) by a start-up company that was one of the first that forsaw the potential of a computer that one uses like a block of paper (with a pen): the GO Corporation.

I could now paint you the picture of this company, but I already made a presentation on that in 2017 (English slides here, recorded German presentation here). The presentation largely follows the 1995 book of Jerry Kaplan (the founder of GO) called “Startup: A Silicon Valley Adventure”. It is a very entertaining book on the specific history of GO, and a good example of how startups work and what troubles they face.

GO incorporates in 1987, and subsequently develops a hardware prototype and an operating system to go with it. It uses an Intel 80286 processor. In January 1991 finally GO presents the Developer’s Release of their operating system called PenPoint. At that stage, PenPoint is already licensed to three other companies, namely IBM, GRiD, and NCR who want to use it on their own hardware developments. You may ask how to develop for PenPoint without GO hardware? Well, after all the prototype hardware is basically only a PC, and you can use several PCs models with specific graphic tablets to simulate the system.

In March 1991, Microsoft (that battled GO on every event stage since years) presents PenWindows, an add-on for Windows 3.1. This allows Windows to be used with a pen instead of a mouse and a keyboard, but (obviously) cannot change the structure of a Windows program in order to adequately support a pen. As a result, users have to e.g. hit UI elements with a pen that are far to small, and have to use the virtual keyboard too often. All Microsoft attempts that use a pen (including Windows CE) fail, and it is maybe this problematic experience that leads to a Microsoft that tries in 2012 to come up with a Windows version that is primarily meant for pen-based tablets although the majority of computers it runs on do not have a pen. This version, of course, is Windows 8.

In June 1991 NCR presents the first tablet that can run PenPoint, the NCR 3125 (proudly designed in Germany). It weighs 1.5 Kg and costs about $4800…

In April 1992 IBM presents the original ThinkPad computer which is a pen-based tablet (and weighs 2.8 Kg). It can run PenPoint. Tablets will not be a hit product for many years (spoiler alert :-), so IBM re-uses the “ThinkPad” trademark for its line of notebook computers (renaming the ThinkPad to ThinkPad 700T so it fits in the overall naming scheme). In case you ever wondered why a Notebook computer is called “pad” without resembling a pad or having a pen…

Apple starts selling the Newton in May 1992. It weighs only 400 grams and costs only $700. Although not sold in huge numbers, the Newton is probably the bestselling pen product of its time.

Where did all this leave the EO 440? And why is it called EO, not GO?

Well, in 1991 GO finds itself choked on the mobile PC market. Microsoft controls the PC operating system market and makes it impossible for GO to find manufacturers for components like BIOS or to sell their operating system to smaller PC manufacturers. The solution seems to be to change the CPU to a RISC model, thus not competing in the PC market. They have two choices: ARM or a chip from AT&T called the Hobbit. Apple just has decided not to use the Hobbit CPU and to switch to ARM for the Newton. When in doubt, GO (as maybe also other startup companies) always decides not for the objectively best option, but for the one they have to use as they are (again) short for money. AT&T, short of a customer for their Hobbit project, offers 10M$ in capital, so they go with the Hobbit (EO will be the only company to ever use the Hobbit and AT&T closes the Hobbit project down some months later).

As another consequence of the deal, GO has to cut out the hardware development division from the company and contribute it to another company AT&T wants to invest in. This new company is called EO (which means GO in Latin…). After that, GO is a pure Operating System company. GO finally releases version 1.0 of PenPoint in April 1992.

In November 1992 finally EO presents their first two models, the EO 440 and the EO 880, but sells them only from April 1993. The design has not the clear, time-less esthetics of the NCR 3125. It is designed by Frog design and has two ear-like protrusions on the top. These protrusions do not have a technical reason, the designers wanted to have them. It has a 7.5″ monochrome display and weighs 1 Kg. This is much handier than the 1.5 Kg of the NCR 3125 or the 2.8 Kg of the ThinkPad, but much heavier that the 400 grams of the Newton even if the Newton has a much smaller display of 5.2″ and can offer only roughly a quarter of the resolution of the EO 440.

The EO 440 sports a 20 Mhz Hobbit CPU and between 4 and 12 MB of RAM. PenPoint is provided on a 8 MB PCMCIA card. The computer offers serial, parallel, PS/2 keyboard, SCSI and VGA interfaces as well as a PCMCIA card slot. The 7.5″ monochrome display has a resolution of 480*640 pixels. Harddisks are optional. The EO 440 cost $2000 initially. There was also an optional mobile phone module which added a handset and an antenna, so you could use your device as some sort of smartphone… The batteries lasted abouth 3h.

The differences of the EO 880 to the 440 are a larger display, a 50% faster clock for the CPU and a much higher weight (and price).

Handwriting Recognition

The key of using a tablet and a pen in the same way as paper was considered to be handwriting recognition. This ability largely determined also the computational needs which exceeded what mobile computers until then had to provide. The handwriting recognition algorithm-wise seems not to have been a problem given enough computational power was provided.

This need was a problem for some 1993 pen tablets, namely the Amstrad PenPad which used a Z80 variant, the Z8S180 at 14.3 MHz and the Zoomer incarnations (e.g. the Tandy Z-PDA) which uses a NEC V20 at 10 MHz. This was the reason for the PC-based pen tablets to start at Intel 80386SL CPUs and for EO and Apple to look at RISC CPUs. For the Newton, every model used a faster ARM chip and early models were known for their sluggishness.

The need for a high computational power drove also the price and the battery requirements, which in turn increased the weight. Therefore, US Robotics’ Palm series of pen-based PDAs later on decided on another design alternative and did not attempt handwriting recognition. Instead, the user had to learn an easily recognizable alphabet (“Graffiti”), so the Palm could use a simple 68000-family CPU. This lead to a cheap, light-weight device that became very popular.

PenPoint as an Operating System

PenPoint supported the following features:

  • Priority-based, preemptive multitasking with processes and threads
  • Interprocesscommunication and semaphores
  • 32-bit flat memory model
  • Ability to run on RAM-only as well as disk-based computers
  • Support of DLLs
  • Heap memory allocation with transparent relocation and compaction (no fixed-length buffers)
  • Object-oriented message passing and subclass inheritance
  • Detachable networking and deferred data transfer
  • All hardware dependencies are isolated into a “machine interface layer” to facilitate porting to a wide variety of hardware and processor architectures
  • Kernel runs on both PC and pen-based machines

User-interface wise, PenPoint programs use mainly (paper) notebook metaphors. You could use tabs to go to a certain part of the notebook, you could have different notebools in a bookshelf, you had tables of contents and so on.

On a page you had the usual means of GUIs of the day: drop-down menus, buttons, scroll margins, the lot.

Also you had a number of commands you could execute with your pen on pages: the pen gestures. You could insert text, remove and edit text, call the options or selecting things.

BTW, PenPoint requires a portrait orientation of the display. Windows wants a landscape orientation. You can typically see for what operating system a computer model is meant when you look at the orientation of the manufacturers logo and the buttons 🙂

PenPoint-based computers are very rare today, the EO 440 is even rarer, and even more so the EO 880. Typically the NiCd batteries are long gone, and sometimes you do not even have a power supply. Some years I was lucky enough to find a EO 440 and last year I could purchase even a power supply for it!

Technical Data

EO 440EO 880
CPUHobbit @ 20 MHzHobbit @ 30 MHz
Display7.5″, 480 * 6409.4″ backlit
RAM4 – 12 MBsame
Portsserial, parallel, PCMCIA, PS/2 keyboard, SCSI, VGAsame
HDD (opt.)20 MB64 MB
Weight1 Kg1.8 Kg
Initial price$1999$2499


Gepard – Part 8: The 3rd life of the Gepard

May 23, 2020

Somewhat unexpectedly another person contacted me and told the story of the 3rd life of the Gepard. This person is Hans Carlos Hofmann. I already read his name before as it appears in copyright notices of some of the later versions of GDOS. As it turns out, he can shed some interesting light on the history of the Gepard after the phases I explained earlier. So, in the following, please find his information (translated from German by me). In the following, “I” means Hans Carlos Hofmann.

I received at that time the source code of the compiler from Mr. Müller as well as license to distribute it as a binary for computers of the Gepard architecture. The reason for that was that modifications of the compiler were needed in order to support MMUs (for the Motorola 68030) and FPUs (for the 68020 and 68030).

I, together with another student, then also developed GDOS further as I had a need for computational power. This other student was Harald Hellmann who developed the data processing for the measuring system for the ion drive at the University in Gießen.

I then used the finished system for my theses in Math and Physics so the system was also represented in the “Experimental Physics II” department (Ion drives were and are a topic in the Experimental Physics I department, translator’s note). At that time I validated a program written by Martin Berz, today a professor (at MSU, translator’s note) that calculated ion optics. The validation took place by comparing the results from his program with the ones from my independant implementation in Modula 2. Thanks to Modula, my implementation was more readable, but could not be run on a CRAY. I’m still a little bit proud in that the most errors could be found in his implementation.

The improved operating system that we called “OS/Science” (you will see in a moment why) received many, partially spectacular modules.

The first module was the interrupt handler. The original Gepards did not do interrupt handling, all the PCBs had was a simple jumper to order the CPU to get an auto vector. A program had to handle interrupts itself. If a program exited, e.g. due to an exception, an active interrupt jumped into nowhere, and you had to reboot the computer. All these problems were solved by my interrupt handler by dynamically creating machine code for the current situation. Using this handler, all the drivers were updated, one by one, so no polling was necessary anymore. This ended up that later applications could stand up to 3000 interrupts per second.

Exploiting this ability a “virtual processor” module (nowadays these would be called threads) was developed that ended up in a preemptive multitasking scheduler offering cooperative multi-user management. The latter features was added due to Modula-2 because else the compiler would have needed modification.

After the Gepard Computer company had ceased to exist, not only HS Computer built Gepard clones, but also the MediSyst company of Prof. Dr. Dimpfel (which existed until September 2005, translator’s note).

With my metrological applications I helped a lot of people to get their PhD, enabling quite spectacular presentations like these ones:

The technology of representing data by dynamically generated code was then used in other modules and applications. One of these applications was a Raytracing program from the begin of the 1990s. It computed an entire day for a single picture and heavily swapping data in and out using the MMU as there was 20 times more memory needed as existed physically. Here are some examples of the generated graphics:

Info Graphics
Visualisation of Atomic Force Microscopy

The “Gepards” were then built until the beginning of the 2000s. New cards were added, e.g. better graphic cards. One Atari (ST)-compatible graphics card could be used both for text and graphics, one that could switch between 1 byte color for every pixel and having 8 different, monochrome pixel layers, and one based on an Intel GDP chip that could execute graphics command in hardware. One big strength of the system was that, already in the 1990s, I could use up to four displays with realtime graphics.

Other things added were a SCSI subsystem for hard disks, tapes, floppy disk drives, optical drives, ZIP drives, CD and DVD drives, photo typesetters, a relational DB, a video subsystem, and a NFS V2 server.

Unfortunately, there was no new CPU/memory board among the new things. HS Computer did develop a Motorola 68040 prototype card, but the design turned out to be unusable due to problems that could not be solved in software. In a system like the Gepard where the bulk of the software is compiled by the onboard compiler, there is this chance to compensate for hardware bugs by centrally providing suitable code generation. The same problems occurred when a 68060 prototype was tried out. MediSyst wanted even to develop a 3 x 68030 + memory card but failed out of economic reasons.

The successor company of MediSyst, MEWICON CATEEM-Tec had the last generation of Gepard-like computers in production until early May of 2020(!). Due to the economic consequences of the Corona virus the now 75-year-old owner of MEWICON (and MediSyst), Prof. Dimpfel has now decided to close his company. Therefore, only a few weeks ago I had the honor to switch off the probably last of the Gepards in production – after over 30 years of Gepards still being used at the one or the other location.

The RANDOC Index: Part 2: Examples

May 1, 2020

Here are some examples of RANDOC Index values for some models as I see them.


model Rarity Specialty Attractivity Impact
C64 1 3 3 4
Atari ATW 4 4 4 1
ZX Spectrum 2 2 3 4
Apple I 4 2 4 2
Mattel Aquarius 3 1 1 2
Canon Cat 4 3 2 1
MCM/70 4 4 3 1
Tatung PC-2000 4 1 1 1

The RANDOC Index: Part 1

May 1, 2020

I like to classify things, and rare and old computers are no exception. Here is my classification scheme for Rare AND Old Computer, the RANDOC Index. As you might know or not know, current prices of old computers fascinate me, and so the Index aims mainly at explaining these prices. My secret hope is that it can also be used for other purposes, but I would not bet on it.

The target of the RANDOC Index is to cluster old computer models according to a number of categories. After having explained the categories in this post, I will give a short list of examples in the next one and try to explain some price phenomena based on the RANDOC Index values of these examples in Part 3.

The RANDOC Index is based on three categories with four values each. As these three categories cannot explain everything, I added a fourth one in case it is needed. This table names all the categories and values:



The “Rarity” category tells us how rare currently a computer appears to be on the market. You can think of it as the inverse value of the supply of a model on the market. It does not say how many units were built. We can safely assume that a model that has been produced in low quantities will never be in high supply on the market, but on the other hand, a rare-but-not-too-rare model with a certain value might be sold more often than a low value model. As this category depends on the market, it can move over time.

When one tries to explain why some models are rarer than others even if the same amount of them were produced, one can have some interesting theories. One (quite probable) theory is that computers meant for industrial or clerical use are much more often scrapped than home computers. That’s why e.g. a Canon Cat (which hides its talents quite well) is much rarer than a Commodore SX64. My favorite theory is what I call “supply retention”. An owner of a computer does not feel the urge to sell it simply because he does not know the price (because it appears rarely on the market) or because the known price is so low that the owner thinks that it is not worth the effort to sell it. A connected theory of mine is the “avalance theory” that says once a model suddenly appears on the market to a price attractive to the owners, it triggers several selling decisions. As a result, a model is not seen on the market for a long time, and then suddenly, some of them pop up in a short period. I always wondered whether one can trigger this by offering such a model on the market without having it, achieving seemingly a certain price, and then be able to buy such a model afterwards 🙂 This would cost only the ebay fee on the achieved price, but you would have to ensure that a) you win the auction yourself (else you are in trouble) and b) that the price is not so high that the ebay fee makes you poor. As it is too dangerous for my taste, I never tried it.

From time to time, also the market changes radically due to technical innovation. When you watch programs like “Antiques Roadshow”, sometimes you hear how different the market pre and post Internet are. When your market is restricted to a country or a region and if you do not really know how many things of a models were made, your perception of rarity might be quite different from a world where things like ebay and a more globalized trade suddenly reveal that a model is much more common than what you thought. For some antiquity types, this drove prices down quite a lot.

The values of the Rarity category are:

The supply of this model is plentiful at all times, and this seems never to change. A Commodore C64 is e.g. certainly always available even in the next 5 years.

available from time to time
These models might not be available every day, but with some persistence you’ll find them offered once every three months. A Sinclair ZX80 might be such a model.

rarely seen
Now for such models, you need some effort. They are not impossible to find, but rarely, maybe once every year, a few of these pop up. An Enterprise 128 might be such a model.

practically unavailable
You have read about these models, you might have seen pictures, and you might even want to own one, but even when you scan ebay for a year you will not find them. Some people have them, but these are probably not the people that will sell these models to *you*. An Atari ATW 800 is currently such a machine.

Technical or Historical Specialty

This category tells us how much a certain model differs from its “run of the mill” competitors at about the same time. This difference can be due to different technical features or because it played a certain special historical role (although sometimes, both aspects coincide or are caused by each other). Once stated (probably with a little bit of hindsight), this value basically stays the same.

The values of this category are:

like any other
This model is no different from the typical model of the era. Basically the same technical features, the same original price, the same historical value. Nowadays PCs (of the same time period) are like any other PC.

a little bit different
For these models, there is at least one clear difference to the competition of the same era. Let’s take the ZX Spectrum. It is technically nothing special at the time, but it packages its abilities in only a few, cheap chips. Therefore, it can be offered for a much lower price. This is the economic difference (coming from a technical difference). As a consequence, it triggers almost single-handedly the creation of a thriving games development industry in the UK.

quite different from average
For this model, there is more than one difference to the competion, but these differences are still within the theoretical technical reach of the competing manufacturers. A Commodore C64 has a better sound than all its competitors and comparable graphics to other top end models, but it offers the entire package to a lower price.

This model has features that change the market. It has not only differences, but these differences has the potential to make the competition look old and to be needed to be replicated by the competition. However, this does not necessarily mean that this potential was fulfilled historically (this information is represented by the “Impact” category). From this point of view the Apple Lisa and the Apple Macintosh were disruptors. The Lisa was famously unsuccessful on the market, and only after the Macintosh got some traction (which took time), all new computers needed a GUI.


This category represents how attractive a certain model is for the market. Therefore, it is a sort of demand (like in supply and demand). Attractivity results from a multitude of factors. Each of these factors typically addresses a different slice of the market, and the more of these boxes are ticked by a model, the more people want to have it. Some of these factors (and their corresponding market slices) are:

  •  rarity
    there are only a few people that are drawn to rare computers. In itself this does not motivate too many people, but as an additional aspect it is important to a lot of people. One example is the guy who collects Commodore computers and wants to differentiate from other Commodore collectors by also owning e.g. a P500.
  • attractivity (and unattainability) at the time when this model was on the market
    One strong motivator to buy a model is when one always wanted to have one, but couldn’t afford it at the time. Now that prices are (maybe much) below the original price and the own income is much higher, the old desire is re-awakened.
  • specialty
    Also for this factor there are relatively few people that buy something solely out of this reason, but as an additional factor, it often motivates people.
  • having it owned at the time (of when this model was on the market)
    Another strong motivator is having once owned a certain model, often when one was young. As a consequence, often positive feelings are connected to such a model and re-owning it might connect one to these positive feelings.
  • other reasons
    Of course, there are many more reasons to find a certain model appealing. Maybe you know one and want to add it in the comments?

This value changes over time. The values of this category are:

(Almost) noone is interested in this model. It was never attractive at the time, maybe it was an industrial model that was never in young ownership at the time. It has maybe no specialty merits, and the current rarity completely satisfies the few people that wanted to have one. In my opinion many generic PCs fall into this category, many yet-another-CP/M machines.

attractive to some
This model ticks a few, not so important boxes. A Canon Cat is not a houshold name and probably not many people knew about it when it was new. However, the connection to Jef Raskin, its technical speciality and its rarity makes it attractive to some people. If you have never heard of this model, that’s exactly my point. If you have heard about it, well, you are the target audience of this blog, aren’t you?

attractive to most
This model ticks some important boxes. A C64 was (almost by definition) never rare, but it was either owned by a lot of people, or wanted by some of the others. It is a historically important computer and has a few technical merits.

attractive to all
This model ticks all boxes or ticks some important boxes strongly. A NeXT Cube is (not very, but quite) rare, it was at all times very attractive, but at the time also very expensive. It is a historically interesting computer, and is of a very attractive design.


This category represents the influence of a computer model on the further development of the industry. It is sometimes needed to explain effects outside the other categories. Also this value stays basically the same.

The values of this category are:

no impact
This value is for models that made no lasting impression on the market. Either because they appeared to early and the market was not yet ready for them or they appeared only in small numbers. Good examples for “no impact” computers are the MCM\70 and the Atari ATW 800. You’ve never heard of them? That’s what I mean 🙂

local impact
Such models had a strong impact in their local market, but not outside. The Micronique series of Hector computers were very well known in France in the 1980s, but outside France barely anyone knew them. Typical reasons for that (as in this case) is that a product is exclusively available in a certain language which is not English :-).

regional impact
Such models had a large impact, but, for some reasons, only on a certain region of the world. A good example are MSX computers. A household name in Asia, but only an exotic appearance e.g. in Europe.

global impact
Such models changed the industry. Either because they were so innovative that the advantages they offered could not be ignored by the competition (like in the IBM S/360 family case) or they came from such a strong competitor that this fact alone ensured market success and orientation of parts of the industry towards it (like the IBM PC).

Now, you might object heavily to some of my examples. First, the values in the categories are not fine-grained, and their definition gives much room for interpretation, and that’s all true, but I wanted to keep the thing manageable. Second, and more importantly, all these categories look at computers purely from a market’s perspective. This perspective changes over time, but it changes even more significantly with different markets, e.g. different countries. A Sinclair ZX80 is much more common in the UK than in Germany.

Intel 4004 μ-Computer (SIM4-01)

April 19, 2020

Some time ago, there was an Intel 4004-based singleboard computer for sale on ebay. The name of this computer was printed on the board: “Intel 4004 μ-Computer”. I did not buy it (also because the price was too high), but I never had heard about it, plus it was based on the first commercially available microprocessor, the Intel 4004. Now, the Intel 4004 is not only well known for its historical importance, but also that it was not really meant to be the heart of a small computer as it was designed to be used in a calculator. So what is this “mu-Computer” contraption?

Intel designed the 4004 as the CPU chip in its 4-chip family from 1971, the MCS-4. The other MCS-4 chips were the 4001 (masked-programmed) 256 bytes ROM, the (80 x 4 bit) 4002 RAM, and the 4003 shift register. The 4003 was meant as the basis to provide MCS-4-based systems output ports e.g. in order to control displays or other peripheral devices. The MCS-4 chips used a 4-bit data bus (although the 4004 supported 8 bit commands). The clock frequency of the 4004 was 500 – 740 kHz.

In 1971 Intel was mainly a RAM and ROM manufacturer who sold only components to their customers. (Mask-programmed) ROMs were ROMs whose content needed to be set during the actual manufacturing of the chip silicon, so a change in ROM contents needed several weeks until a new ROM with the new content was available. This was of course a problem for the software developers because they could change their software quickly, but then had to wait weeks until the new version could be used. Therefore, also in 1971 Intel announced a new product, the first EPROM. This was a ROM type whose content can be changed in a matter of minutes as it was stored in a re-writable manner on the chip (EPROMs are the chips with the glass window in the middle and often a sticker on top of that window). So, developers could program their system, create a new version of their software on their system, and when the software was stable, a traditional (and much cheaper) ROM could be produced without the need of many iterations.

Therefore, Intel felt the need to support developers using their MCS-4 products with first, a development system based on the MCS-4 that accepted either ROM or EPROM chips and second, with an EPROM programming device that allowed to load new content to an EPROM (an EPROM burner in today’s technology). The first development system is the 4004 μ-Computer. “mu” like the greek μ sign for “micro”. How did that device look like (that later on basically every CPU manufacturer would produce and sell for promoting their own design)?

The 4 large sockets on the top left corner can hold either a ROM or an EPROM chip each. The small chip on the bottom left corner is the 4004 CPU (tiny because of the 4 bit bus), and the 4 sockets to the right of it can hold a 4002 RAM chip each, giving it a whopping maximum of 160 bytes of writable memory. The other chips on the board are not really interesting (at least from my point of view). I read that the board actually has no 4003 chip on it, probably because there is no real standard design in a MCS-4 computer for it as this depends on what devices you want to connect. There are no recognizable interfaces on the board, just an edge connector of no recognisable standard at the bottom. So how do you connect something to this card? Meet the Intel MCB4 (Micro Computer Connector Board) chassis:

The chassis (the box on the bottom helds an 4004 mu-Computer on the front slot, and the second device, the EPROM burner on the back slot. It offers some switches, some lights, some interfaces and one (E?)PROM socket. You connect a TTY to the chassis, and voila: an entire microcomputer, ready to use.

Now, if you looked at the first picture and wondered where it said “mu-Computer”, well it doesn’t, it says “SIM4-01”. This is the (slightly) later name for the board. See, the problem was that Intel did feel that it was a component manufacturer, not a producer of computers, and that it should not be perceived (especially by its computer manufacturing customers) as such. Therefore, after some management thinking, this was not the 4004 micro-computer, this was the MCS-4 simulation device (SIM4-01), and you will find it much more often under that latter name. If you are interested in the history of the 4004 mu-Computer and especially the aspect of Intel shying away from being perceived as a computer manufacturer, I can wholeheartedly recommend the excellent article of Zbigniew Stachniak on exactly this topic (see [Stachniak] in the references).

The 4004 mu-Computer was probably the first computer with a 4004 CPU, the first microprocessor. Therefore, one can probably also call him the first microcomputer (if its definition requires a microprocessor). It (and its descendants like the twin brother SIM4-01 and the younger, healthier brother SIM4-02) can even be the only historic, commercially available, programmable computer with a 4004 CPU.

Technical Data

Manufacturer: Intel
Model: 4004 mu-Computer (a.k.a. SIM4-01)
CPU: Intel 4004
ROM: 4 sockets for 256 bytes Intel 4001 ROM, or 1701 or 1702 EPROM each
RAM: 4 sockets for Intel 4002 RAMs (80 x 4 bit = 40 bytes each)
Interfaces: 72-pin edge connector, allowing for 6 I/O ports (2 in and 4 out), and TTY
Released: 1971
Initial price: ???


The Value of a Computer over its Lifetime

April 13, 2020

I’m currently in the process of compiling a presentation on “Collecting Old Computers as a Hobby” for the upcoming VCFB 2020 event. I’m not sure whether it really fits in that presentation, but I made a highly speculative, subjective chart on, what I think, the value of a computer over its lifetime looks like. Here it is:


Let me explain. First, I differentiate the lifetime of a computer into 4 phases.

The “phase of usefulness” starts when the model comes onto the primary market, i.e. when it’s new. Obviously, the manufacturer thinks that it will be bought because it offers some benefit to the buyer. It is sold at the initial price (which typically will decrease over the time the model is offered by the manufacturer). I think it is not unreasonable to assume that the value of the computer, once bought, drops exponentially in this phase, especially when it it a state-of-the-art model. As it approaches the end of the usefulness phase, it typically drops to a more symbolic value that is basically determined by the minimum amount a seller is willing to accept in order for the entire transaction to make sense at all (i.e. compensating for the effort of the seller to offer, handle, and sell the thing. If the offered price would be any lower, it would not be worth the effort of the seller to do anything. If this computer model was bought originally by a company, it is most probably written off since some time anyway, to the company cannot put any value on it. The length of this phase depends probably on different factors, but maybe something like 10 years is not completely wrong for a computer. This phase transitions into

The “garbage phase“. The computer has no usefulness anymore, but it is not so old already that there are sentimental feelings connected to it. In this phase, the value is minimal and probably quite stable around the symbolic value I tried to establish in the last paragraph. Maybe in this phase it is not handled by the original owner, but by traders who specialize in surplus goods, making the price of the computer maybe even a tad lower because such traders are more efficient at low prices. I put a length of this phase also at around 10 years and try to substantiate that in the next paragraph, because the next phase is

The “sentimental phase“. This phase has a lot to do with the average age of a typical collector of a computer. Typically, they either had this computer model when they where young, or they were around when this model was fresh on the market. Since this phase probably 20 years or more has passed and they remember this time in retrospect with positive feelings (who does not remember his/her youth with joy? The music was much better than nowadays, the world was not that complicated and there was much less hatred and selfishness in the world). Also, being his his/her late 30s, 40s, and early 50s, things start to settle down for yourself. Often, there is less shortage of money, and less time needed to find a partner. For sure you don’t have a midlife crisis, but all this urge to buy a motorcyle… 🙂 Now, this is the time to feel young again with the dream machines of your youth, to fulfill unfilled dreams of owning cool stuff for a bargain. As a result, people start collecting computers. This process starts slowly, only a few people start collecting, but now the prices raise again. More and more people collect computers, maybe collecting becomes cool, and , with the raising prices, maybe even a good opportunity to invest money.

My theory is that the prices of a computer a collector wants to buy are:

  • not dependent on the initial price
  • dependent on a bunch of other factors, e.g.
    • how rare the model is
    • how many other collectors the model want
    • and, almost more importantly, what the buyer is willing to pay for a sentimental, or decorative, or conversation piece

I have also the impression (although I did not invest time into this to prove it) that these new values are clustered (and I put some estimation of how large these clusters are in the figure). Also, these price clusters increase over time as inflation and salaries increase over time. Finally, people think that the prices will go up forever and start thinking of them as investments (which will draw in also non-collectors that will act as investors).

This phase ends when the majority of the collectors starts getting so old, cool stuff from one’s youth is getting less important. This happens when no younger collectors replace the old ones, e.g. because the age of computers being cool stopped at some point. There are some areas where new collectors seem to continously “re-grow”, e.g. art and antiquities. There are other areas that flourished over many years, but suddenly came to a lack of collectors, e.g. stamps. My assumption is that, as computers became utilitarian in the 2000s instead of being fresh and not understood by parents, they aren’t as magical to millenials as they are to earlier generations (this is probably different to consoles and game-related computing, these will probably thrive much longer). If my prediction is correct, then prices at the end of this phase will drop dramatically as the market vanishes and the budget per collector gets much smaller.

It is also no clear to me what the next phase after the sentimental one is, and how this changes the prices for old computers.

In summary, here some conclusions:

  • most computers have their highest value when they are sold initially
  • the best phase to buy an old computer is the garbage phase (which is long gone for computers up to the year 2000)
  • do not buy old computers as a long-term investment

So, here you have it, my wild, highly speculative look into a crystal ball. What do you think?

BURP – Basic Using Reverse Polish

March 21, 2020

Recently, I did not buy a new old computer. I did not buy it because I was outbid in a real auction in the UK (by twice the amount I was ready to pay, not to mention the 33% fee on that price for the auction house and the VAT, nor the additional cost to package and ship the whole thing). However, I am very ok with not having bought it, because it would have been a kit computer of unknown state, there wasn’t any documentation with it, and it featured only a Z80 CPU. The only three redeeming qualities of this model are its rarity, its use of a mathematical co-processor, and its unusual programming language. So, I decided to proceed as if I had bought the computer, and write about the programming language.


The computer was a Powertran PSI COMP 80 computer (sold for 420 GBP + commission). It is a relatively early (1979) design published by the British magazine Wireless World and used as a basis for a singleboard computer sold as a kit by a British company called Powertran. Z80 CPU, 8 kB of RAM and EPROM, 2 kB of video RAM, monochrome graphics of 128×64 pixels or 64×32 characters: not an usual design for that time. What made this model a little bit special was the use of a mathematical co-processor, a National Semiconductor MM57109N.

But let’s start at the programming language of this computer. It is called BURP, “BASIC Using Reverse Polish”. The reverse polish notation is the thing where you first specify the parameters of a function (which are pushed on a stack), and then you specify the function name. When the function is called, it takes its parameter from the stack, calculates the result, and pushes it back on the stack. This is the (still quite exotic) basic principle in Forth, some early HP pocket calculators, and Postscript. So, if you would write something like add(10,33) in any conventional programming language (requiring a parser to translate this code into something a computer understand), in reverse polish notation that would become “10 33 add” with the semantics “put a 10 on the stack, then a 33, then call the add function, who will take the two parameters from the stack and put the result (43) back on the stack for the next function to use”. This notation allows for quite compact interpreters, but the programmer has to manage the stack herself.

I like Forth a lot so I thought, ok, this is funny, a BASIC with a reverse polish notation should be quite quirky, ending up in programs like ’10 “Hello, World” print 20 10 goto’ if this type of basic also supports line numbers. However, BURP is even more strange than that because not all commands use the reverse polish notation, but only expressions. The rest of the syntax is still conventional infix notation.

All this strangeness has a reason: the mathematical co-processor. As [Carver] puts it, “The constraints of the MM57109, which was essentially a dedicated calculator chip with a 4-bit microcontroller interface bus, strongly affected the design of the language. Significant features of the language include a fixed set of 26 numeric variables (A-Z), a maximum of 256 lines of code, a three-deep hardware stack for expressions, a limit of one for-loop at a time (so no nesting, not even in GOSUBs) and no string processing (except implicit concatenation of static text and numbers during output.)” Oh yes, plus the MM57109 talks to the world in reverse polish notation.

Ok, so the number calculating part of this BASIC by and large represents the format which the math processor needs. So, how does a BURP program looks like?

Example: LET C = 3 SQ 4 SQ + ROOT

Here, we assign a value to a variable C. This value is SQRT(3^2 + 4^2). First, the 3 is put on the stack. Then, a “squared” operation is called on the 3, replacing it by 9. Then, the 4 is put on the stack, and then replaced by 16. Now, and add function adds the 16 and the 9, replacing it by 25. Finally, the square root is taken, so in the end, the only number of the stack is 5, which is assigned then to the variable C (actually put in register C of the math chip).

The National Semiconductor MM57109 (the original data sheet titles it as a “Number Cruncher Unit”) is from 1977. It is the mask-programmed derivate of the MM5799 chip, which is the 2-chips-in-1-version of the 5781/2 chip set, the calculator chip family of National Semiconductor. It added 70 mathematical functions to the MM5799 design. From the viewpoint of a computer manufacturer, this is very attractive, because a) you don’t have to write all this math code yourself, b) it is efficiently executed. However, the MM57109 was not really an FPU (floating point unit) like modern math co-processors (which are nowadays integrated into the CPUs). First, the unit processed numbers that came in up-to-8 decimal digit packets (coded as 4-bit BCDs). Second, “Instruction execution times range from 1 ms to 1 second” (according to the data sheet). ONE second. That makes total sense for a calculator, but not too much sense for a computer. However, “real” FPUs did not exist much before 1977, with AMD’s AM9511 being one of the first.

So, here you have it. An early kit computer with a calculator chip as a mathematical co-processor and a crazy BASIC that makes complete sense in this design. Burp. Happy digesting.


Canon object.station 41

March 8, 2020

1989 Canon bought 16.6% of NeXT, Inc. for $100 million. Canon also produced the MO drives that the early NeXT models were based on and also served as NeXT’s distributor in Japan. 1992 Canon added another $30 million (other sources say $55 million) to this sum in order to keep NeXT afloat. In 1993, NeXT decided to exit the hardware market and to become a software-only company.

It is not clear why Canon did the next step, but probably Canon thought that their investment in NeXT might be in danger. NeXT might not feel being a hardware company any longer, but certainly Canon was (and still is). NeXT would take care of the OS side, so why not produce hardware especially suited to the NeXTStep OS, but at the same time chosing a less exotic architecture, thus saving development cost? This might have been the thoughts of Canon when they bought a license from NeXT to use NeXTStep on their hardware (they seemed to try to get even the NeXTStation brand to use for their models, but failed).

Canon and NeXT were even in negotations about both buying NeXT’s Fremont factory as well as some hardware development department, which at the time, was developing an 88000-based NeXTStation. However, we know that the factory was not sold in the end, and so was probably also the development department (because else we might have seen a different machine).

What Canon ultimatively came up with was a PC architecture. It was certainly high-end, with SCSI-2 and a quite full set of features, but it was also a machine you could install Windows NT on (and I mean the Intel version). This is not to say it was a completely ordinary, unmodified PC, because there are some peculiarities.

But, sorry, I completely forgot to introduce to you the topic of this post: Meet the Canon object.station 41.


As mentioned before, this computer has a conventional PC architecture, albeit with a more high-end set of components. It uses an Intel 486DX mit 100 MHz, has 16 MB of RAM (up to 96 MB), an integrated 500 MB SCSI harddisk, a CD-ROM drive and a 3.5″ floppy disk drive. It came pre-installed with NEXTStep 3.3. It had also Insignia’s SoftPC pre-installed, so you could use PC programs from NEXTStep. I think this is very funny, with the machine being a PC… It came with a Logitech PS/2 mouse and a PS/2 keyboard that included NeXT-specific keycaps, controls for audiovolume and monitor brightness.

The only special thing the computer has is the graphics system. It is not a mere graphics card, but a proprietary Canon architecture based on Chips & Technologies Wingine technology. It is a 64200 Wingine together with a modified Brooktree Bt485 RAMDAC to support the internal 4-4-4 color representation of NEXTStep and had 2 MB of VRAM and up to 1280 x 1024 16-bit color resolution. The hardware had been optimized to be between 15% and 30% faster than a standard Intel Pentium PC running NEXTStep. The CD-ROM delivered with the system therefore did not only had the NextStep on board, but also drivers for Windows NT.

Blake Patterson wrote in a 2007 BYTECellar blog post about the Wingine: “WINGINE was designed by Chips & Technologies to be an extremely high speed framebuffer requiring motherboard support in the form of a C&T chipset and a proprietary local bus WINGINE slot into which the WINGINE graphics board was inserted. This made the system one of the preferred graphics configurations for NEXTSTEP, as the operating system did not employ any 2D graphics acceleration – all it wanted was an extremely high bandwidth video subsystem. (Graphically intensive NEXTSTEP was the first OS to feature “solid drags” of windows which, at the time, was a rather heavy lift.) […] The WINGINE also utilized expensive, dual-ported VRAM as opposed to cheaper DRAM for optimal speed.” Epson and JCIS were two manufacturers who offered motherboards featuring the Wingine local bus slot.

In the object.station 41 however, the graphics is directly contained on the proprietary Canon motherboard. In the local bus slot there is a riser board, and in the VL bus slot of the riser card the SCSI-2 card (a Buslogic BT-445C VL-Bus controller) is contained (parallel to the motherboard. The riser card allows for the small height of the pizza box case, and contains 3 ISA slots.

The object.station 41 was not the only member of the family. Allegedly, there was also an object.station 31, and a 50 and 52. The 31 from 1995 had the same case, but was missing the SCSI-2 card. The 50 and 52 introduced in 1995 had Pentium processors and seem to come in black mini tower cases that do not look different from any other case. The 50 seems to have a 100 MHz Pentium and the 52 a 120 MHz Pentium. I’m not sure whether the 31, 50, and 52 models were sold at all or in numbers. There is one photo of probably a 50 out there, but that’s basically it. The least rare model is the 41.

The model I have unfortunately misses the harddisk and the CD-ROM drive, but I think this might be less of a problem.

The Canon object.station series seems to be very unsuccessful. I’m not sure whether there is a point in asking why because the better question should be: Why should it have been successful in the first place? NeXT did not develop hardware anymore because it sold badly, NeXTStep 3.1 was available for HP’s PA-RISC CPUs, Sun’s SPARC, and for PCs, and the modifications Canon added to a standard PC architecture weren’t exactly killer features. There was simply no reason to buy an object.station. And so an object.station is a very rare find, much rarer than any original NeXT hardware.

Technical Data

Manufacturer: Canon
Model: Object.Station 41
CPU: Intel 486DX4@100MHz
RAM: 16 MB (up to 96 MB)
Resolution: max. 1280×1024
Color: 16 bit
Interface: Fast-SCSI-2, Ethernet, parallel, 2 * serial, keyboard, mouse, video, microphone, headphone, stereo out
Drives: 500 MB HDD, CD-ROM, 3.5″ floppy disk drive
OS: NEXSTEP, Openstep, Windows NT
Released in: 1994
Initial price: $5000



Unusual Sony Notebook Drive Bay Modules

February 29, 2020

It is not completely unheard of to have a modular bay system for notebook computers, having the possibility for the user to chose whether to have an optical drive there, or maybe an additional battery, or the like.

But I think that there was a decision meeting missing after a brainstorming session at a Sony computer department when they came up with these additional bay modules:

PCGA-CWN1 Compact Woofer

Yes, this is a woofer. It works because it seems that the bays were open at the bottom:


PCGA-TKN1 Number Pad

Yes, it is exactly what you think it is – an additional number pad you can flip out of the bay:


And, no, these were actual products, no photoshopped fakes.

Not crazy, but also quite unusual is this bay module:

PCGA-MDN1 Net MD drive

Yes, that’s a MiniDisc drive for a notebook.


NCR Safari 3115

February 27, 2020


Recently, on ebay, I stumbled upon another NCR mobile, pen-based computer. In contrast to my beloved 3125s, I have never heard of it.

It looks like the older, smaller, much uglier brother to the 3125, but it is not. It is the much rarer, smaller, much uglier, younger brother of the 3125: the Safari 3115.

“Safari” already hints to the time it was released, because Safari is the family name of the AT&T mobile computers. NCR was taken over by AT&T in 1991/92, so this release must be later than that.

Now, the model designation 3115 puts it in the NCR 3000 family, below the 3125, but the “3000 family” was always a marketing lie as the computers in it differ a lot architecture-wise and OS-wise.

The operating system of the 3115 was Windows 3.1 with pen support. The RAM seems to consist of a DRAM card that is accessible via the interface bay. Mine is a Samsung 4 MB model. It is labelled “ICMC V4.1” which is the same as PCMCIA 2.0.

There is an “unofficial NCR (Safari) 3115 support page” which holds most of the information on this machine, but it seems to updated last in 2000…

It weighs 1700g, so it is even 200g heavier than the A4-sized 3125… And although the outer area of the 3115 is smaller than the one of the 3125, the outline volume is probably about the same or even larger!

The Computer History Museum even has a docking station called “CommStation” for the 3115.

I did not think that this machine even deserves more research, because, boy, it is ugly, and because there were a lot of Windows-based pen tablets out there after 1991.

However, I opened the case to see what’s inside because some things (like the concrete CPU model) are not even known. And I have to say, the inside is more advanced than what I thought it it would be.


What I was surprised first was the fact that the computer seems to be at least splash-proof. There is a thick seal in between the case halves, and most of the interfaces are put behind rubber plugs. There is not even an electric interface connecting the machine to the docking station, but an array of infrared LEDs.

The second suprise was that most of the weight seems to be contained in the display which is secured in a metal case. The PCB is not very large, the case not that heavy.

The final suprise was the “harddisk”. It is not a harddisk, it is basically the second generation prosumer-grade SSD in form of a SunDisk(sic!) SDI-20 20 MB SSD with a date of 1992-1993. The first generation was developed by SunDisk (now SanDisk) for the original IBM ThinkPad in 1991. It had a capacity of 20 MB and costed $1000. Obviously, an SSD is much more suited for a rugged pen-based computer than a rotating harddisk.

Other things I found inside were: an Intel 80486SX CPU and 4 MB of soldered RAM.

So, here is my final verdict: This was an attempt to created a rugged, small, pen-based Windows tablet. Unfortunately, it is way too heavy and ugly. Although I don’t know the original price, it probably have not been cheap. It is more interesting that what meets the eye and it is a very, very rare thing.

Technical Data

Manufacturer: NCR
Model: Safari 3115
CPU: Intel 80486SX@25 MHz
RAM: 4MB (8 MB max)
HDD: 20-40MB
Weight: 1700 grams
External dimensions: 23cm*23cm*7cm
Pen: Cordless 1 button digitizer pen made by CalComp Inc, transmits on R/F ranges 0.0576Mhz and 0.0614Mhz, runs on 4(E 393 buttoncell batteries)
Display: 6.25″ Backlit Monochrome VGA
OS: MS-DOS 5.0/Windows 3.1 with pen support
Interfaces: 1 RS232C DB9 serial port, 1 Centronics 25-pin Parallel port, 1 PS/2 Keyboard port, 2 PCMCIA-II expansion slots, 1 PCMCIA-1 memory card slot, 1 Infrared communications/docking port, 1 external power/charging connector
Battery: 9.6V (NIMH) 1200mAh, 1.2A, good for 4hrs per charge?
Released: 1993
Initial price: ???