View Full Version : SCELBI 8H now running BASIC!

October 18th, 2013, 06:40 AM
Thanks to Mark Arnold, who stripped down SCELBAL to the barest fundamental elements, I now have BASIC running on a reproduction SCELBI 8H with 4K of memory. As far as I know, BASIC hasn't been run on an 8H before. Mark, who created SCELBAL back in the mid 70′s calls his new stripped down version of BASIC, “tiny SCELBAL”. He removed all non-essential features, including support for floating point math in order to make it fit into 4K. There are only about 350 bytes for program space left in a 4K SCELBI 8H, but that is enough for some very simple games. I have ported a version of HILO from Ahl’s “BASIC COMPUTER GAMES” book. I’ll be making a video, posting source and object files very soon. I’ll also post the source of HILO and describe some space saving tricks.

Mark says SCELBI considered doing this back in the 70′s, but determined the result would be too limited to be useful for most practical purposes.

This implementation should be portable to other 8008 machines, with at least 4K memory, such as the Mark 8.

-Mike Willegal

October 22nd, 2013, 04:47 PM
Now that is a rather interesting old computer. Uses the 8008! wow where can I get one? Are there any retro kit available to build your own?

October 22nd, 2013, 05:04 PM
Now that is a rather interesting old computer. Uses the 8008! wow where can I get one? Are there any retro kit available to build your own?

I think you can go to Mike's web site and find out more, order stuff, etc:




October 23rd, 2013, 05:57 PM
Hey that's cool thanks smp for the linkage!

October 24th, 2013, 08:03 AM
I'm gonna go ahead and ask the dumb question. The scelbi had another name didn't it? Was it the Mark-8 or am I just thinking of something wrong? I thought for a second it was like the Kenbak but the pic certainly looks more like a Mark type creature.

October 24th, 2013, 11:49 AM
Actually an interesting question.

Both the Mark 8 and the SCELBI were both based on the 8008 and were multiple board systems that used similar form factor PCBs, though the underlying designs had significant differences.

The SCELBI was advertised first in QST magazine in March 1974 by company founders, Nat Wadsworth and Bob Findlay. SCELBI offered bare PCBs, kits, built up system and a number of I/O expansion options that could be connected to it's 6 input and 8 output ports. SCELBI eventually came out with the SCELBI 8B with 16K of memory and support for PROM based monitor, editor and assembler. The SCELBI 8B could run SCELBI's own SCELBAL floating point BASIC, though this BASIC was also ported by a few people to Mark 8s with expanded memory. In it's heyday, the SCELBI was considered the system to get. That is, if you could afford it, as it was an expensive choice.

The Mark 8 was a designed by Jon Titus, and first announced in an article in July, 1974 Radio-Electronics magazine. Jon only sold PCB boards through a partner PCB manufacturer. The builder had to source their own components. A mini-industry did start up to support the Mark-8, including a monthly newsletter published by "mini" computer hobbyists, which also had some coverage of the SCELBI and other systems.

The Altair, with it's much more powerful 8080 processor and low price, pretty much put an end to both systems commercial viability. Both Jon Titus and SCELBI ended up moving successfully into publishing.

Mike W.