Replica IBM 5150 PC motherboard

[Fred Cisin]

On Thu, 8 Mar 2018, Ali wrote:
>> Howzbout the Fischer? diagnostic ROM, thta came with a hard-wired
>> configured serial port, that could perform some tests on a system that
>> did NOT boot to the point of video.
> Now that does sound interesting. Tell us more uncle Fred ;).

Not much to tell, and I don't know much.
I think that it was Todd Fischer.
He supplied a ROM, and a serial board that was hard configured for a 
terminal (can't run software to configure a serial card if the machine 
won't boot!).  It therefore did not rely on the video working.
He also had been selling cases and power supplies for 5.25" drives at the 
conputer swaps.


I really enjoyed the P.O.S.T. cards.  In debugging code, I could insert a 
simple output to a port of the value of a variable, with minimal 
disruption of any of the rest of the code.


A friend pointed out that most diagnostic software, including many memory 
tests, etc. would not run if there actually WAS a fault, such as bad RAM 
in Bank0. 
So, as a joke, he wrote a "DIAGNOSTIC PROGRAM", that put "It works!" on 
the screen.  "If you get the message, then it means that everything is at 
least sorta working.  If you do not get the message, then something is 
wrong."  Later, he changed it to "friendlier message", and had it say, 
"Hello, world".