Differences between PDP-11/83-84 M8190-AB/AC and AD/AE CPU cards
bqt at update.uu.se
Thu Feb 5 08:22:28 CST 2015
On 2015-02-05 15:00, Pete Turnbull wrote:
> On 05/02/2015 13:10, Noel Chiappa wrote:
>> The 11/84 backplane has two special Q22/CD slots after the processor slot
>> which the memory goes in, with the CD sections wired to
>> through-connect the
>> PMI pins.
>> I have this sneaking suspicion that the Q22 portions of those two
>> slots aren't
>> _real_ QBUS slots (so you can't plug a QBUS device into them if you
>> using them for memory :-), because I suspect they didn't run BIAK and
>> BDMG to
>> those slots, but rather piped them directly to the UNIBUS adapter
>> slot. My
>> reasoning for that is that if you don't plug in a memory card in one
>> of those
>> slots, you don't have to plug in a grant continuity card, so....
> But you're supposed to plug in a Minimum Load card, aren't you? I
> wonder if those slots would work for a non-DMA device.
Yes, and no.
You should plug in a MLM if you haven't fully populated the slots.
They are not wired up as Qbus slots.
>> > I seem to remember that when two memory boards are used, they
>> should be
>> > the same.
>> Really? That would surprise me.
> I don't believe that's true. It's certainly not true in an 11/73 or
> 11/83, and I suspect the idea comes from one of the 11/84 manuals, which
> only mentions one type of card (half- or fully-populated).
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