Remember when I was bitching about the S-100 having half a dozen or more signals, any four of which would do the job? That's only true if the FP, the CPU, and the target memory or peripheral agree on which signals those are. That's not always the case. Some cards seem to prefer you use one pair of signals as the active strobes with others as qualifiers, while others require the concurrence of all before anything happens. It may be that the memory doesn't think it's being written, or that it doesn't believe the data is being gated onto the bus. You might find it illuminating to reach in with a scope probe and see how long the write and the select strobes are at the destination, and compare them with the source. Dick -----Original Message----- From: Bill Sudbrink <bill(a)chipware.com> To: Discussion re-collecting of classic computers <classiccmp(a)u.washington.edu> Date: Thursday, July 08, 1999 4:58 PM Subject: RE: IMSAI (moving along...)