31 Dec
2012
31 Dec
'12
7:38 p.m.
Daniel Snyder wrote:
[Snip]
NOTE:
-----
NONE OF THE FOUR MSV11-J MODULES CAN BE PLACED IN A Q/Q
BACKPLANE SLOT. IF THIS IS ATTEMPTED PERMANENT DAMAGE WILL
BE DONE TO THE BOARDS AND TO THE SYSTEM.
THANK YOU for this post and the above vital warning!!!!!!!!!!!!!!!!!!!!!!
While it would have been unlikely to attempt to use an MSV11-JD or MSV11-JE
memory board in that fashion when they should be reserved for use with
the PMI
memory function activated, at a point when it was just easier to pick up
a board
that was right at hand, it might occur. I assume that the above warning
is with respect
to magic smoke appearing if an MSV11-J board is ever placed into a Q/Q
backplane
slot such as what is present in a VT103.
One other example of damage occurring after placing two boards into two
adjacent
Q/Q slots is the two board 18 bit controller set for the RL01 / RL02
drives. The
M8013 / M8014 boards MUST NOT BE PLACED INTO A TWO ADJACENT
Q/Q BACKPLANE SLOTS. IF THIS IS ATTEMPTED, PERMANENT
DAMAGE WILL BE DONE TO THE BOARDS.
I have not seen this warning anywhere, but it was experienced first hand
around
20 years ago.
[Snip]
Although the MSV11-JD and MSV11-JE are PMI memories they can be
used in
two other Q-bus configurations.
1. If either of these two memories are used in slots 1 and/or 2 of
a Q/CD backplane such as the H9276 (BA11-S box) or in the
MicroPDP-11 BA23 backplane, and with the standard 15MHZ KDJ11-B
cpu (non-fpj compatible) in slot 3, the system will perform PMI
memory cycles. In the case of BA23 backplanes, a maximum of two
memory modules may be used in slots ahead of the processor,
with
a minimum of one memory module in front of the processor still
functioning as PMI memory. In the case of the H9276 backplane
a number of MSV11-JD/JE memory modules may be used ahead of the
processor bringing the system to a full 4MB of PMI memory.
This first configuration for the Qbus BA23 box is the standard expected
placement of the memory boards and exactly why they were manufactured.
2. If in a Q/CD or BA23 backplane the memories
reside in slots 2&3
with either of the KDF11 or KDJ11 processors in the slot 1
the MSV11-J memories will respond as standard Q-bus
memories,
performing normal Q-bus and block mode memory cycles. This use
of the MSV11-J memories is also true for the MicroVAX
cpu.
However the fact that the MicroVAX I cpu is a two board set
requires a slightly different configuration. Slots 1&2 will be
used for the MicroVAX I cpu boards with only one memory card
used, that being located in slot 3 for the BA23 backplane and
one or more memory cards being used for other Q/CD
backplanes.
The only constraint with either of the second configurations is
that in the BA23 or other Q/CD backplanes no module may be
placed adjacent to the MSV11-J that uses pins in the CD
connector. Instead leave an empty slot between the MSV11-J and
this option. An option which does not use the CD interconnect
may be placed adjacent to the MSV11-J.
I notice that this warning does not appear in the same BOLD LETTERS
as the first warning. While there is no guarantee, it seems likely that no
damage to the system or the boards will occur, but rather a lack of correct
operation of the system.
Likewise, I tend to assume that the lack of any warning of placing an
M8190-AE board into a Q/Q (ABAB backplane such as is present in
a VT103) is also acceptable.
In almost every case (except where there is an explicit warning against
doing so - of course that warning would have to be known and so
caution is probably best in all cases), all quad Qbus boards which operate
by themselves are able to exist in either an ABCD slot or an ABAB slot.
Otherwise, DEC would have been forced to manufacture two options of
each board when the BA23 backplane was introduced with 3 slots at the
top being ABCD and the other 5 slots being ABAB serpentine. Since
I know of only two examples (one of which I learned about less than
30 minutes ago), I feel that it is likely there are few, if any, additional
examples.
Jerome Fine