On 02/04/2019 11:20 AM, Fritz Mueller via cctalk wrote:
The MMU classifies the error in register SR0; this decodes to a segment length
error (access within the segment beyond configured bound). As Noel notes,
however, this is not consistent with the instructions we see at the point of
fault.
OK, so the CPU presents an address that is within the
segment bound, but the MMU declares it to be OUTSIDE the
bounds of the segment. That could be a CPU problem, but
likely would be the same with the MMU on or off, so the
diags SHOULD catch that. But, if the CPU is sending a good
address, then it has to be the MMU is failing on the
addition/comparison with the segment size.
Anyway, is it possible to borrow an MMU from somebody else?
Potentially... It is a two board option; I do have a spare for both of the
boards, but these spares each are in need of other repairs at the moment.
One slightly complicating factor is that I have a *very* early 11/45. Most of
my boards (including the MMU boards), as well as my backplane, pre-date the
currently available schematics on bitsavers, etc., and there are no records
regarding which ECOs have been applied on my hardware. Thus my interest in
tracking down ECOs/FCOs... I've been picking my way through the list that Jay
recently posted, verifying by looking at the greenwires which FCO's I have
applied and which not. Its a bit painstaking.
This could be messy, but DEC was FAIRLY good at making
updates backwards compatible where possible. So, it MAY be
true that a later MMU will still work in this CPU.
Jon
