IBM XT diagnostic ROM

der Mouse mouse at Rodents.Montreal.QC.CA
Wed May 28 07:58:34 CDT 2008

>> How the heck is a diagnostic ROM going to diagnose a dead CPU?  I
>> must be missing something here...

Well, if it's a little more than just ROM but fits in a ROM socket, it
could, for example, notice a lack of read cycles.  If it's enough more
than ROM it could run a CPU emulator and notice that it isn't obeying
the instructions it's fetching (though that's hard to do right, since
the ROM socket doesn't see things like interrupts or RAM).

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