Parasitic Engineering Clock Mod

Discuss construction, troubleshooting, and operation of the Altair 8800c computer

Parasitic Engineering Clock Mod

Postby TheoAU » August 25th, 2022, 1:53 am

I made an interesting discovery today. I was browsing the download section of the Deramp site and I came across the Parasitic Engineering clock fix for the early Altair CPU board:

https://deramp.com/downloads/altair/har ... clock_mod/

Looking at the pictures I quickly realized that this mod looks familiar. It's been done on my original CPU board. See pics below. At IC Q, you can clearly see the 94618 IC installed. And on the back of the CPU you can also clearly see the mod. The name of this mod was familar, and I believe I might have the orginal documentation for it.

Does anyone have any background knowledge of this mod? I just thought it was interesting considering all the discussions about clock issues with the newer CPU boards. And also considering that my original CPU has it.

I did a Google search on this IC and aside from the Deramp link, there's no other results.
Attachments
20220701_192117.jpg
20220701_190926.jpg
TheoAU
 
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Re: Parasitic Engineering Clock Mod

Postby Wayne Parham » August 25th, 2022, 9:10 am

Nice call-out. Thanks for bringing fresh attention to this mod.

I think I'll build a CPU board with this mod and compare it with a stock board to see what differences it makes. I don't have as many boards as some of you do, but I do have several and I have an 18-slot system in addition to a 9-slotter. So it sounds like I'll find a lot of idiosyncrasies in a stock system are solved with this mod.
Wayne Parham
 
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