Intel MDS Series II IOC question

Tony Duell wrote: Today in a failed attempt to repair the IOC board, I resurrected some ancient hardware. The IOC board is the back panel board on an Intel MDS Series II that handles most of the I/O of the system. It does a lot! It is based on a 2.4MHz 8080A cpu. Well, I broke out an Intel ICE-80 and hooked it up. This is the first In-circuit emulator that I know of, perhaps the first ever. It is quite primitive, but it can do a lot in the hands of a skilled operator. If I ever find such an operator, maybe I will be able to fix this damned IOC board!!! One of the problems I encountered with the emulator is because the RAM in the target system is dynamic. I think that when the emulation "breaks" from a breakpoint it seems that the RAM loses its contents. Perhaps the refresh circuitry relys on a clocking cpu. But it does look like I get inconsistent results reading the ROM on the IOC board. So I will now look at the buffer chips and maybe the address decoding. I tried to map the execution memory to the host MDS (that is the machine that is hosting the ICE-80), but since that slows execution and there are some software timing loops that didn't work very well. I am making progress, slowly. And putting two of these beasts together (one working one for the ICE-80 host, and the "target" system that needs to be fixed) isn't trivial. They weigh about 100 pounds each!!! It was a comical scene, though, with two MDS Series II systems side by side. I thought my table was going to colapse and the lights dimmed when I turned them on. ;)

Stay tuned...I have some more disassembling to do. Dave