This project is about an ISA riser card for the Prodest Olivetti PC1 personal computer but it may very well work with other old XT style computers with a regular 8 bit ISA slot!
They can be ordered online at dirtypcbs.com if you are interested in getting a pack of 10 or alternatively at my Tindie Store.
The circuit is 1:1 for every pin in the original ISA slot being expanded to the two slots on this card. The only components are four 100uF/16V electrolytic capacitors near the slots.
The following pictures show the top and bottom layers of the PCB.
It has been brought to my attention that I forgot to enlarge the tracks for B5, B7 and B9 (-5V, -12V and +12V) and that they are not thick enough to carry currents in excess of 100mA without starting to heat up. This can be a problem when connecting ISA cards that draw high current from those lines.
However we also need to remember that the PC1 does not provide power on B5 and B7 (-5V and -12V respectively) so this is only a problem if you use a card that requires +12V from B9 and internally regulates it to whatever voltages it needs. If you really need to draw a lot of current from B9 (+12V) you can solder a small wire from the pad to the pin of the socket as a last resort solution.
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You can order this board yourself at dirtypcbs.com or alternatively at my Tindie Store.
Published on Tuesday 2016/11/08, last modified on Sunday 2022/05/29
Motivation and overview