Mark-8 Clone project

[mwillegal]

The SCELBI 8H preceeded the Mark 8 by a few months. LIke the Mark-8, it supported 4K of SRAM using 1101 spread across 4 boards. It was followed a year later by the 8B which supported 16K of SRAM (2102) and/or EPROM (1702) also spead across 4 boards. The EPROM board could be ordered with MEA programmed into it. MEA was a complete integrated development environment and was used to develop SCELBAL BASIC for the 8008.

Actual power on the 8H is about .6 AMPs on the -9 volt rail, per 1K SRAM board. A 4K system would require about a 3 AMP -9 volt supply. Here is the text from the SCELBI HW manual.

THE BASIC SCELBI CARD SET CONSISTING OF ONE EACH OF: SCELBI #1100 CPU CARD, SCELBI #1101 DBB & OUTPUT CARD, SCELBI #1102 INPUT CARD, AND SCELBI #1104 FRONT PANEL CARD; REQUIRES A MAXIMUM OF 1.5 AMPS AT +5 VOLTS AND 100 MILLIAMPERES OF -9 VOLTS.

EACH “PAGE” OF MEMORY IN THE SYSTEM (256 WORDS) REQUIRES 200 MILLIAMPERES OF +5 VOLTS AND -9 VOLTS.

I use 5 or 6 AMP 5 volt supply for both SCELBI 8H and 8B.

regards,
Mike Willegal

 

[snuci]

The Bill-1 looks really neat. Have you attempted to fire it up yet?

No, not yet. I want to save what is on the EPROMs first and have an ME1702A programmer that I am building. I need to get back to that as it's been on the back burner for a bit.

 

[falter]

Got some vintage ICs today:



They appear to be legit. I'm stunned I found 8263s of the correct vintage. The RAM I'm not sure -- there's no obvious date codes, which if I read correctly means they are pre-73 (I read Intel started doing date codes that year). I'm not sure if a Mark-8 builder in the day would have used RAM that dated 4 or 5 years prior... but I guess it's better than being into the late 70s-early 80s.

I also got a bunch more late 8263s. So I now have 11 of them. I thought that chip was really going to be a bear to locate.