On Sun, Sep 27, 2020, 3:08 PM Noel Chiappa wrote: > > So that confuses Q22 memory. If one tries to use one with an LSI-11, > > the machine is totally dead - not even ODT. > > Oh, that's another LSI-11 'feature' (only discovered after someone sent in > a > help request on CCalk for a dead LSI-11): if there's no working memory at > 0, > ODT won't start/run. So if the Q22 memory is confused, the whole machine > is dead. > Maybe a bit of electrical tape over the fingers on the 256KB board would keep them isolated from these signals? That would help determine if it is just floating pins, or that the LSI-11 used these pins for other reasons? Warner