5 Feb
2015
5 Feb
'15
5:59 a.m.
On 2015-02-05 14:10, Noel Chiappa wrote:
I also would not expect the frequency to be a problem. However, as the
Qbus/PMI differs from the 11/84 CPU bus, there can be chips that don't
work correctly in one or the other.
I actually know where I read up on that. The 11/84 system manual
documents the CPU bus, including differences.
Check
http://www.textfiles.com/bitsavers/pdf/dec/pdp11/1184/EK-1184E-TM-001_Dec87…,
chapter 2.2, which both documents the PMI bus, and in which way it
changes when it sits in an 11/84.
I might have also read some other manuals that give me information, but
this was the quickest I could find right now.
One obvious difference, by the way, is the fact that when you have a
Qbus system, memory must sit to the right (top of) the CPU in order to
use the PMI bus, while in an 11/84, the memory sits to the left (below)
the CPU, while still using a modified PMI protocol.
As other have pointed out, Jerome is not correct.
Right. The 11/84 backplane is wired differently. The CPU goes in the
first slot in an 11/84 system.
And slots 2 and 3 are not Q-CD slots.
Not true. You can put a two meg and a one meg card into the system
together. Done that in the past. Works just fine.
Johnny
--
Johnny Billquist || "I'm on a bus
|| on a psychedelic trip
email: bqt at softjar.se || Reading murder books
pdp is alive! || tryin' to stay hip" - B. Idol
From: Henk
Gooijen
Maybe a few PALs have to be a faster version, but
I do not expect that.
The 15 MHz to 18 MHz is not that big of a difference.
I did wonder about that, but they boards use parts from a number of different
chip companies (both the PALs, and the PROMs), so since I don't know how to
read those parts for speed variants, I couldn't say. From: Johnny
Billquist
The 11/84 variant is pretty much a PMI bus all
the way, but I seem to
remember a couple of signals defined differently even in the 11/84
compared to the 11/83.
If you run across where you saw that, I'd be curious. The 84's use is, as you
point out, different, since it includes the CPU<->UNIBUS adapter protocol for
UNIBUS cycles. But I would have assumed that it was a plain superset of the
83's (not that I have read much about 11/83's... :-). From: Jerome
H. Fine
The MSV11-JB (1 MB) and MSV11-JC (2 MB) are used
in the PDP-11/84. The
MSV11-JD (1 MB) and the MSV11-JE (2 MB) are used in the PDP-11/83.
Err, not sure this is correct: I got an 11/84 with an MSV11-JD in it. As
someone pointed out in a later message, the difference between the B/C and
D/E is that the B/C only work as PMI memories, their QBUS functionality has
some issues (IIRC, something to do with QBUS block transfers not working
correctly). In addition,
for at least the PDP-11/83, the PMI memory must be placed
into the backplane ahead of the CPU for the memory to function as PMI
memory. That may be the only position allowed for the memory for the
PDP-11/84.
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 aren't
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.... Anyway, I
have a spare 11/84 backplane, and one day I'll get around to poking at it with
an ohmmeter to verify that suspicion.
Correct. They are *not* qbus. Don't even try plugging any Qbus cards in
there.
I seem to
remember that when two memory boards are used, they should be
the same.
Really? That would surprise me.