Johnny Billquist wrote:
"Jerome H.
Fine" <jhfinedp3k at compsys.to> skrev:
Rod Smallwood wrote:
>Now that makes a lot more sense.
>So PMI memory choice is: (2 Max)
>MSV11-JD M8637-D 1 MB ECC PDP-11/84 or PDP-11/83
>MSV11-JE M8637-E 2 MB ECC PDP-11/84 or PDP-11/83
Jerome Fine replies:
I am not absolutely positive, BUT the probability is VERY
high that the above two PMI memory boards are ONLY for the
Qbus. I believe that you must use either the MSV11-JB or
the MSV11-JC within the PDP-11/84 system.
Good catch! I didn't think of that
one. Yes, you're right. In fact the
-JD and -JE don't even claim to be PMI memory, but just plain Q-bus
memory (according to the field guide). That's definitely not useful.
You need the -JB or -JC.
Jerome Fine replies:
The MSV11-JE can be used as either normal memory when installed below
the CPU or as PMI memory when installed above the CPU. Since I have
actually used this board in both positions, I can absolutely confirm this to
be true for a Qbus BA23 or BA123 backplane. When used with a KDJ11-Bx
CPU (the quad board) and the MSV11-JE is below the CPU, under RT-11,
the CPU is reported as a PDP-11/73 and the memory is NOT noted as being
PMI memory. When used with a KDJ11-Bx CPU and the MSV11-JE is above
the CPU, under RT-11 the CPU is reported as a PDP-11/83 and the memory
is noted as being PMI memory. When using 2 of these boards with the
switches
set correctly, 4 MBytes of memory is available. When I used 2 of these
boards,
I only used both above or both below the CPU. While I doubt that there
would
be any permanent damage, I recommend that it not be tried, i.e. one
board above
the CPU and one board below the CPU.
In my experience, I have always read that the MSV11-JD and the MSV11-JE are
ONLY for use with the Qbus. If anyone has successfully used either
board with
a PDP-11/84, that would be helpful information. I strongly suggest that
without
extremely reliable confirmation that these 2 boards always be limited to
use ONLY
with a Qbus system and in particular in an ABCD slot. On the other
hand, Peter
Turnbull states in his post of today that the above is NOT true. I have
also
replied to Peter's post asking him to be absolutely sure, i.e. "Peter
have you ever
used either the MSV11-JD or the MSV11-JE with a PDP-11/84 system?"
I have also read that the MSV11-JB and MSV11-JC are for use ONLY in a
PDP-11/84 system. If anyone has successfully used either board in a Qbus
system either above or below the CPU, that would be helpful information. I
strongly suggest that without extremely reliable confirmation that these
2 boards
always be limited to use ONLY in a PDP-11/84 system. Peter Turnbull
confirms
this warning.
It is probably
confusing, but the CPU is the KDJ11-BF which
is used in BOTH the PDP-11/83 (which I have and the memory
used is the MSV11-JD or the MSV11-JE) and the PDP-11/84
which you have. If you can find a KDJ11-BF along with two
MSV11-JC PMI memory boards, the cost will likely be much
less than a PDP-11/94 CPU.
That is probably correct as well. The 11/9x cpu boards
are scarce and
expensive. The 11/8x cpu boards are more common and reasonably priced.
I AGREE!!!!!!!!!!!
As far as my testing was able to show, the PDP-11/93 CPU
is only about 10% faster than the PDP-11/83 CPU when it is
used with PMI memory. Consequently, just about the only
reason to use the PDP-11/93 CPU is when the reduction in
the number of boards is critical such as when a BA123 is
being used (with 4 ABCD slots and 8 ABAB slots) which can't
be expanded. Equally, either a single BA23 (with 3 ABCD
slots and 5 ABAB slots) or a dual BA23 (with 5 ABCD slots
and 9 1/2 ABAB slots - the last 1/2 ABAB slot is lost and
the first ABCD slot is lost the the connecting boards and
cable) can also have the same problem.
I tend to assume that the speed difference between a PDP-11/94
system and a PDP-11/84 system is also only about 10%, but I
have never tested either system.
My usual speed test under RT-11 is to compare 7000 blocks
of the VM0: device against itself. I used to have both
numbers, but I can at least get the time for the PDP-11/83
if anyone wants.
The PDP-11/83, 2 MSV11-JE boards and 2 DLV11-J boards uses
4 quad slots while a PDP-11/93 uses only 1 quad ABCD slot
or between 1 and 3 less slots depending on how much memory
and DLV11-J boards are used. In addition, if 4 MBytes of
memory are essential and only 1 additional quad slot is
required, there are 3rd party 4 MByte PMI memory boards for
the Qbus, i.e. just one quad slot is needed. I have never
been that short of slots.
I have also read that the MSV11-JD and MSV11-JE boards should
NEVER be used together. Can anyone else confirm or deny this?
I suspect that 3 * MSV11-JD boards may be used in a BA123 box
with 4 ABCD slots, but since I don't have any MSV11-JD boards,
let alone 3 of them, I can't verify this. Obviously, even in
a BA123 box, a maximum of 2 * MSV11-JE boards are used.
Please ask if there are any questions.
Sincerely yours,
Jerome Fine
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