Intel MDS Series II IOC question
dmabry at mich.com
Sat Sep 3 23:30:58 CDT 2005
Tony Duell wrote:
>I am certainly interested, even though I don't have one of these machines.
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
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.
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