PDP-11/45 RSTS/E boot problem

Noel Chiappa jnc at mercury.lcs.mit.edu
Mon Feb 4 12:24:40 CST 2019

    > From: Jon Elson

    > Does the MMU classify what the error condition was

Yes, there are a series of bits in SSR0 to indicate the particular error:
'non-resident', 'length', 'read-only', etc (and also the segment number the
error's from).  As my message mentioned, we're seeing the 'length' error bit
on, and for segment 1 (which the instruction isn't using).

    > is it possible to borrow an MMU from somebody else?  

Fritz does have a spare board, but it has known errors. We haven't thought about
borrowing one yet, it may come to that.

    > If this fault could be caused by memory

Well, _some_ of it could. E.g. if the 'jsr r5, csv' is read as 'jsr r4, csv',
dropping the '1' bit in the register number, that would explain the wonky R5
content - R4 does contain the 034 that should be in R5, I have just noticed.

But that doesn't explain the bogus MM trap. Although I suppose there could be
several different problems, all at the same time.

    > does this machine have a cache? 



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