80286 Protected Mode Test

[Rob Jarratt]

I have a DECstation 220 (Olivetti M250E) which is failing POST on a "simple
test of the 80286 protected mode". It says in a service manual I have that
for this test the CPU is set in the protected mode, the machine status word
is checked to see whether it indicates the protected mode and then exits
protected mode. This test seems to be failing. Is there any possible
explanation for this other than a failed 80286 CPU? Could there be any
external reason? This board suffered some battery leak damage. Clearly the
80286 is working well enough to execute this diagnostic and send some text
to the screen, so it basically works.

 

Thanks

 

Rob