S/23 machine update card

Dennis Boone drb at msu.edu
Sun Aug 18 18:38:13 CDT 2019


I've determined that the piece of my S/23 that's causing the power
supply to blow its 12V fuse is the machine update card.  The manual says
this provides additional R/W storage for microprogram updates.  That
sounds like something that wouldn't be necessary for normal operation.


1. Can anyone confirm that I'm not losing anything by just pulling this?

2. Anyone have a cross ref for the IBM house numbers on these chips?

3. Anyone have a spare card they'd part with?

4. As long as I'm dreaming, anyone have a set of BRADS floppies or images?

Machine update card photo:

Interestingly, the underlying PCB for this seems exactly the same as the
one for the word processing feature card.

Many thanks,


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