"Bill Sudbrink" <bill(a)chipware.com> wrote: Hi Bill I'm sure there is a scrambling of this connection someplace. This is the only place that can do the things you mentioned. The front panel is hard wired to the S-100 bus. This means that wires can't get mixed here. The data lines from the CPU board to the front panel can get swap around. Remember that the way the front panel does things is by jamming instructions and data directly onto the CPU's bus through the cable. The results are read from the S-100 bus. In other words, when you use a front panel switch, like examine, it forces a jump instruction into the CPU with the address you specify with the switches over the cable, in sequence. A real clever trick I'd say. You'll note that the C3 bit sequence still works if the data bits 7-0 are mirrored to 0-7. This is why the panel seems to do anything at all. If reversing the ribbon connector in the header doesn't work, try removing the socket from the CPU card or front panel and installing it on the other side of the PC board. I would suspect that this was an error in the construction of the front panel from day one. It is most likely the front panel that is backwards. Just flipping the IDC header on the cable won't mirror the wiring to the connector. Putting the socket on the other side of the board will mirror things. At worst, you'll have to hand wire the cable to make up for a non-standard connector but I'd think it was more likely just getting the header socket right at both ends. I don't have a schematic of the panel in front of me but it is a simple mapping problem. Dwight