SCELBI 8H Usability Reasessment

For a long time, I would say that the SCELBI 8H was the first practical computer marketed to the general public. The key word being practical, as certainly many of the other personal computers of the day, were not very useful machines, other than for educational purposes, at least without adding additional capabilities to them.

From the time that I got my reproduction SCELBI 8H working, I’ve been able to demonstrate a number of interesting, practical applications on it. That I was able to do so, was justification for the claim that a SCELBI 8H was a “practical” computer. However, I’ve always used a second computer to assemble the source code and then downloaded the application to the SCELBI through a serial port. A few months ago, when I talked to Bob Findley, I asked about how they did application development for the SCELBI 8H. It turns out that Bob and Nat used almost exactly the same approach that I used. Only thing is that they used a PDP-8 as a platform for the cross assembler and a teletype with it’s paper tape punch/reader to download the program to the SCELBI. Though the cross development platforms are different, what Bob and Nat did, was essentially the same as what I’ve done.

I’ve come to realize that though you can run some interesting, practical applications on the SCELBI 8H, it really can’t do it, without either help from a host computer, an impractical amount of time, or the addition of features like a built in monitor. After talking to Bob, and thinking about it a bit, I guess I’m ready to say that though the SCELBI 8H, as shipped, can run practical applications, it was not a very practical stand alone computer. However, that still doesn’t remove the significance of the SCELBI 8H as the first offering from one of the very first personal computer startup type companies.

Note that the limited capabilities of the 8H were recognized by Nat and Bob, who developed the follow on SCELBI 8B, with it’s extensive built in software suite. More about the 8B in a follow on post.

4 Responses to “SCELBI 8H Usability Reasessment”

  1. Jack Rubin says:

    If you can come up with the PDP-8 cross-assembler, I’ll trade you a PDP-8 for a SCELBI kit! Would Mark Arnold or Bob Findley have access to it? Very cool, especially considering the photos of Nat’s PDP-8/E!

  2. Marco says:

    Interesting comment, but I remember back then writing applications for my Kim-1 with only pen and paper… couldn’t this also have been possible for the SCELBI?
    By the way, are you still demonstrating your SCELBI unit at VCF West this weekend? For some reason your name was taken off the exhibitors list…

  3. Mike says:

    You can program the 8H with the front panel, but just to get an idea of how difficult it is to use, before I added the EPROM monitor, it took me 10 to 15 minutes to enter the 37 byte boot loader that I wrote. Sophisticated programs, would be extremely difficult to get up and running and require extensive amounts of free time. Sorry, I will not be at VCF-west this year.

  4. Len Bayles says:

    Hi Mike,

    Having lived through that era and cut my teeth on the 8008 I appreciate your comments. I think for those of us who were early experimenters a lot of the fascination was just knowing that we had a “real” computer at our disposal. Knowing what we were going to use if for was a second thought. I remember demonstrating my 8008 for friends and neighbors. I would painfully flip in a simple monitor program that would allow me to enter keystrokes from my kit built SWTPC keyboard and then be displayed on a TVT. To me that was absolute magic! I’m not sure my audience had the same appreciation that I did.

    I bought a copy of Scelbal but never did get it loaded on my system. About the time I was planning to build a cassette interface I instead bought a ZX81. I still have the copy of Scelbal and plan on running it on my Mark 8, once I upgrade the memory, and my Scelbi. (Thanks to your lovely boards.)

    Once interesting thing is that I don’t know that computer development is completely different today. It’s true that you have a full suit of SW available on modern computers. Although cross development is still very alive and well in many areas of computing. The Scelbi being highly restricted on the peripheral side is not totally different from today’s headless computers.

    I think we have been very fortunate to have experienced a good chunk of modern computer history. It has much like watching the growth and expansion of the Internet from a small research network to what we have now.



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