18 Jun
2013
18 Jun
'13
7:32 a.m.
On 17 June 2013 17:15, Pete Turnbull <pete at dunnington.plus.com> wrote:
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.
Yep, so most probably I'd get a BA11-N (or -S), whose backplane would
be replaced with the H9275A I already happen to have on hand.
Though, PSU alone is also something I'd not mind. As I did have a
silly idea of a steampunk PDP-11... backplane, PSU and custom control
and distribution panels in a nice Victorian style
cabinet/box/end-table thing, with a reskinned (to clear plexiglass and
brass) Model 35 KSR teletype bolted to the top.
Though, I'd rather stick a teeny-tiny QBUS '11 in that as opposed to a
"proper micro-mini".
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.
Yes, I have heard about about the BA11-S, though I don't know if it'll
play host to the H9275 backplane.
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 :-(
Yeah, I'm not in the UK, though I am in the Comonwealth. (Canada to be
general; Hamilton/Stoney Creek, Ontario to be specific.)
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.
I am a fan of neither BA23 box; the deskside one looks a bit too much
like a rather large, rather generic deskside workstation PC, the
rackmount one, well my only real gripe is: "Why is it *beige*?"
Or at least, most of the ones I've seen are beige. If they came in the
same "clean" white as the BA11 boxes, I'd not mind the rackmount one.
(The two 5.25" bays would make life easier. Otherwise, I'm currently
trying to figure out where I can stick a 3.5" SCSI hard disk, and one
of those lovely "Aztec Monster" SCSI CF card readers.)
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.
DHU11 is UNIBUS not QBUS; the DHQ is the QBUS equivalent. Of course
there are third party boards; but I'd like to limit my number of third
party boards (to the CMD CQD-220A/TM; because I've personally never
seen a DEC made QBUS SCSI board).
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.
I don't really plan on running an KD11 of any sort in this system, nor
a KDF11; but I do want to try and stick with a QBUS only (no CD
interconnect at all) backplane. While I do miss out on some of the
older quad-width card sets (RLV11 and RKV11 come to mind), chances are
they wouldn't work with a KDJ11 system at all.
Plus there's the fact that my current processor and backplane are
wholly incompatible (DEC documentation are quite thorough in the whole
"DO NOT PUT PMI INTO QBUS EVER" warning schtick). So, I'd rather
"downgrade" the processor (18MHz to 15MHz, and no PMI), then have to
deal with finding PMI memory (and using a BA23, or multiple BA11-S
boxes, with bus expander cables).
Cheers,
Christian