80286 Protected Mode Test

Fred Cisin cisin at xenosoft.com
Sat Mar 6 17:16:39 CST 2021

A stupid idea:
Could the test require, and be failing, access to memory above 1M?

On Sat, 6 Mar 2021, Rob Jarratt via cctalk wrote:

> 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

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