17 Jun
2013
17 Jun
'13
2:15 p.m.
On 17/06/2013 17:40, Christian Gauger-Cosgrove wrote:
One of the DEC module lists on the web lists that a
BDV11 with board
revision E or higher already has said ECO applied to it.
Indeed it does.
How common are 22-bit capable BDV11 modules, per
chance?
I've never knowingly seen one, but then I've only seen 10 or 12 BDV11s
altogether, at least closely enough to note the rev level.
All I've got is that KDJ11-BF CPU,
a naked H9275A backplane, and am in the process of getting a CMD
CQD-220A/TM. But more on this later on in the e-mail...
As I'm trying to recreate the PDP-11 system I "lost", I'm trying to
stick with the equipment that would work best in a BA11-N box. Which,
in this case, is an H9275A backplane, as opposed to the H9278
backplane of the BA23.[1][2]
So you need a box anyway... A BA11-N would more usually have a H9273
straight backplane. I suspect you'd be more likely to get a box
complete with backplane and PSU, than just an empty box.
And as Dave Riley pointed out, you could also opt for a BA11-S, which is
similar, except it has a 22-bit H9276 backplane, a beefier (but
otherwise very similar) H7861 PSU, and a different label: it's a
stick-on black affair on a BA11-S. I don't know for sure if it has the
embossed 11/03 badge underneath, but it certainly feels like it on my ones.
That's why I'm openly asking whether
"downgrading" from an 11/83 w/FPU
to a dual-wide 11/73 with FPU, a boot-ROM board, and a DLV11-J would
be a worthwhile trade to anyone.
If you were near York, UK, I'd volunteer :-) I could also find you a
box and memory, though more likely a BA23 then a BA11 :-(
[1] As I mentioned I'm trying to replace my old
PDP-11 system which
was, ahem, "lost." So I'm trying to get a BA11-N box, mostly because I
find I don't like the aesthetic of the BA23 box.
Good enough reason. Is that because it's normally a deskside which
looks like (and seems to weigh as much as) a storage heater, or is it
just the layout? Because there is a rackmount version, sans skins. I
must admit, though, we have a shared preference here. If nothing else,
it's easier to get at things in the back of a BA11. And it's not so heavy.
H9275A is completely Q22/Q22 serpentine (means a more
densely packed
system, since I don't even want to deal with PMI at all; plus it is
compatible with KDF11 processors, without wasting space).
I see the point about wasting space if you want a lot of dual-height
cards. Four DHQ11s plus CPU and the rest makes nine, even without disk
or bootstrap/terminator, but at the same time you're limiting the
quad-height boards that could be useful, because there are some that
won't work in a serpentine backplane. Your choice of tradeoff, though.
32 serial lines? Two DHU11s? Just a thought; there are options.
Beyond that, I'm not entirely sure what you're getting at here. I
expect you know that just because a particular CPU board supports PMI
and so does a backplane, doesn't mean you have to *use* PMI. Put the
memory under the processor instead of above, and even PMI memory works
as plain old QBus memory. Nor are there any common backplanes that
don't support a KDF11 (both dual- and quad-height 11/23, 11/23+) or even
KD11-F/KD11-H (LSI-11, LSI-11/2, 11/03) -- though with KD11-F/H you want
to be careful what else might use the BDAL18-21 lines on a 22-bit backplane.
--
Pete Peter Turnbull
Network Manager
University of York