Found these inside a non-working 71B

[Dave Frederickson]

U10 you ask? There's no U10 on the schematic.

No, but it's clearly on the PCB, right where Mike installed the Math ROM there is a footprint for a 6th internal memory module. The schematic is missing some parts.

It looks like there's some funny stuff going on with the higher numbered pins on that part as there are a number of connections between the pins and also the pins on U9. In addition, the other version of the PCB (with the golden zebra connector) is wired differently!

So what's U10? I think it's for the Debugger ROM mentioned in the IDS.

Dave