I haven't played with mine in a while, but was reminded of this by a comment in a current ebay auction. Whenever I put a Cromemco 16FDC or 64FDC in an IMSAI box, the front panel stops working (the 4FDC doesn't do this). Looking at the schematics for the Cromemco boards, I can't see any reason for this, but watching the behavior of the FP lights, it looks like the board is driving the data bus whenever a wait is asserted. Can somebody else with the 16FDC or 64FDC schematics take a look? Thanks, Bill Sudbrink