Jerome H. Fine jhfinedp3k at compsys.to
Fri Jun 3 11:11:43 CDT 2016

 >Rod Smallwood wrote:

> >On 03/06/2016 16:43, Jerome H. Fine wrote:
>> >Rod Smallwood wrote:
>>> [Snip]
>>> 4.  I have what I believed is a working 11/83 in my computer room
>>> 5 . I'm going to try my processor in there and yes I know about PMI 
>>> and  the backplane.
>> Just a bit of information from what I seem to remember - I hope
>> the information is correct.
>> The M8190-BF board I have supports:
>> (a) PMI memory placed ABOVE the CPU
>> (b) Non-PMI memory placed BELOW the CPU (I never
>>     attempted to place non-PMI memory ABOVE the
>>     CPU)
>> (c)  When the PMI memory was placed into the backplane
>>       BELOW the CPU, then the memory would act as
>>      normal non-PMI memory.
>> Under RT-11, the command:
>> will conclude that the following CPU is present:
>> (a)  PDP-11/83
>> (b)  PDP-11/73
>> (c)  PDP-11/73
>> So other than when PMI memory is placed BELOW the CPU
>> as in (c) and it therefore takes longer to access the memory, I don't
>> think the question of PMI memory will really make any difference.
>> Jerome Fine
> Hi its a KDJ11-B all memory on CPU board
> Rod

I am very confused.  Is your mention of memory on the CPU board
for the PDP-11/83 or the PDP-11/93?  I thought that the PDP-11/83
never had memory on the CPU board (assuming that the cache is not
regarded as memory).

This aspect of the thread is probably no longer relevant, I just wanted
to note that PMI memory can be used with what most individuals would
consider to be a PDP-11/73 (naturally a quad) board and the PMI
aspect of the memory will be activated when the PMI memory is
installed ABOVE the CPU board.

Also when PMI memory is installed BELOW the backplane, it is then
used as normal Qbus memory in a Qbus system.  I can't see anyone
doing that, but it is allowed.

Jerome Fine

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