On Jun 5, 7:28, Ethan Dicks wrote:
> --- vance_at_neurotica.com wrote:
> > Hello people. Is there any way to tell if a backplane is QQQQ or
QQCD by
> > looking at it, and without having to pull the backplane out of the
> > chassis?
> In some older chassis, you can see the backplane wiring, but not on
> boxes like the BA23 or BA123.
>
> > What if I can find the model number of the chassis?
>
> That's useful... The model numbers that look like BA-23, BA-11N,
BA-11M,
> etc., are the ones you want.
>
> Also, remember in newer boxes, it's three slots of Q22-CD, with the
> rest Q22-Q22.
That's true for a BA23 (3 slots plus 5), but in a BA123 it's four Q-CD,
eight Q-Q, and the thirteenth slot is not bussed at all.
> Older boxes can be wired for either 18-bit or 22-bit addressing,
> which may or may not involve Q-CD slots. I _think_ the BA-11N is a
> 18-bit Q-CD box... that's what I remember my 11/23 is in (but I
> added the extra wires some time ago to make it Q22).
Yes, a normal BA11-N is Q-CD. So is a BA11-S.
If you can read the H92xx number off the backplane (it's often visible
without too much effort, for example it's on the top of a BA11-M/N/S
backplane) you can look that up to see if it's straight (Q-CD),
serpentine (Q-Q) or mixed.
The following is not exhaustive, but includes the common ones:
PDP-11/03 BA11-M H9270 18-bit 4 x Q-Q
PDP-11/23 BA11-N H9273 18-bit 9 x Q-CD
H9275 22-bit 9 x Q-Q
PDP-11/23+ BA11-S H9276 22-bit 9 x Q-CD
microPDP-11 BA23 H9278 22-bit 3 x Q-CD, 5 x Q-Q
H9281 18-bit various sizes, only two slots
(AB)
microPDP-11 BA123 54-17507
or 70-22019 22-bit 4 x Q-CD, 8 x Q-Q, 1 x non-bus
DDV11 18-bit 9 x Q-Q, slots EF are separate
Q-Q backplanes are usually referred to as serpentine (or sometimes as
zig-zag), Q-CD as straight. Serpentine slot order goes like this:
slot 1 ----> slot 2
|
V
slot 4 <---- slot 3
|
V
slot 5 ----> slot 6
etc
Some of the backplanes have optional jumpers to enable/disable LTC
interrupt, or for termination. Many carry the SRUN_L signal only on
row 1. Beware of such differences when changing backplanes or linking
two together. The DDV11 is unusual in being hex-height instead of
quad-height; the extra slots are nor bussed, except for +5,V, 0V, and
-12V, but may carry odd voltages, depending on which OEM or
experimenter last used it!
There's a rumour that the first 3/4 slots in a BA23/123 are special and
you can't use them for anything except memory or processor; that's
rubbish, they're normal Q22-CD slots and you can put anything that's
Q-CD compatible in them, so long as it's after the processor. What
*is* special is the range of PMI memory boards; if you put them in
*front* of a KDJ11-B they use the CD interconnect for the Private
Memory Interface
but if you put them *after* the CPU they use the Q-Bus like all other
memory boards.
--
Pete Peter Turnbull
Network Manager
University of York
Received on Thu Jun 05 2003 - 16:28:00 BST