Zane H. Healy wrote:
Q2) Do all
empty slots need to have bus grant boards?
No, you need them when you break the
"Snake". As long as you have them in
the looping pattern anything after the last card can be blank. Of course
the trick is knowing how the pattern goes, and I can't remember. It varies
depending on the backplane you have. IIRC, you've got a BA123, and the
first three slots have to have either a Quad board, or only a double board
in the top, after that it starts snaking with the fourth slot. IIRC, the
fourth slot starts at the top.
Jerome Fine replies:
BA123 has 12 slots:
01 A / B / C / D |
02 A / B / C / D \/
03 A / B / C / D |
04 A / B / C / D \/
05 A / B / A / B - > - >
06 A / B / A / B < - < -
07 A / B / A / B - > - >
08 etc.
09
10
11
12
13 reserved for RD5n and RX50 or RX33 I/O distribution boards
With a uVAX, I understand you place the CPU at the top (which is
furthest away from the from of the BA123 box where the drive
bays are located) and ALL memory (a maximum of 3 boards - they
MUST be in the A/B/C/D slots and connected to the CPU via a
cable. NOTE: Maximum memory for uVAX is 16 MBytes.
With a PDP-11, the usual place for the CPU is in the top
slot with the memory to follow - EXCEPT FOR THE 11/83
If you have a dual board in slots A/B of 01 to 04, you MUST
leave the C/D portion empty.
If you have a missing or open A/B in slots 05 to 12, you MUST
insert a bus grant - an M9047 is a bus grant. Normal Qbus quad
boards (EXCEPT FOR THE RQDX1) have a built in bus grant
to take care of things for this backplane. You do NOT need
a bus grant card after the last card in the backplane.
IF you are using an RQDX1, it MUST be the last card in the
backplane since it has NO built in bus grant. It does not have to
be in slot 12, there just can't be any boards which follow AND
require a bus grant.
The BA23 is almost identical, except that there are ONLY 3
A/B/C/D, and there are 5 more for a total of eight AND there
is a very different I/O distribution panel for RD5n.
Ask if you need more!
Sincerely yours,
Jerome Fine
RT-11/TSX-PLUS User/Addict
