1 Feb
2002
1 Feb
'02
8:42 a.m.
On February 1, Gunther Schadow wrote:
I read a web article the other day where the guy
describes the
various forms of the Qbus and he also said that you could fry
certain cards when you stick'em in a wrong version of the Qbus.
This is indeed correct...if you plug an RLV11 into a Q/Q backplane
instead of a Q/CD backplane, for example, you'll let out the magic
smoke.
Since I have a uVAX II and a PDP11/03 I would want to
know if
I can mix and much cards with thoese busses or if I would fry
a K[ZF]QSA board sticking it into the wrong bus.
Dunno about the 'QSAs in particular...but in general things should
work, except for cards with 16/18/22 bit address issues.
Also, why was the need for grant continuity cards an
advantage?
It's not an "advantage" per se...just what the bus needs. Several
busses use schemes like this...for example, with some high-speed
peripheral controllers in VME Sun systems, you need to remove the BG3
and IACK jumpers from the other side of the backplane. There are no
grant "cards" but there are indeed grant jumpers.
The OMNIBUS didn't need it but the UNIBUS (and
Q-bus?) do.
Omnibus is a "straight" bus...pin 1 goes to pin 1 on all slots, pin 2
to pin 2, etc...there are no hardware-prioritized "daisy-chain"
signals like those found in some other busses.
Also, what's the deal about grant continuity
cards, they seem to
just have a few lines shorted. In the UNIBUS box next to my
VAX 11 it has some intermediary open slots but only one grant
card plugged in. How could that work? Also, why can you stick
If those slots are all straight Unibus, it likely WON'T work. :)
1x or 2x cards into the different sections, is there a
difference
where you put them? Why is the feed to the UNIBUS only a 2x card
and where must you plug that? Is it magic?
SPC slots..."small peripheral controller" I believe is the correct
expansion of that acronym...you'll want to grab a pdp11 unibus
processor handbook for that info...it's all in there.
Are there UNIBUS backplanes with more than 9 rows?
None that I've seen. I've seen 4- and 9-slot ones.
-Dave
--
Dave McGuire
St. Petersburg, FL "Less talk. More synthohol." --Lt. Worf
2 Feb
2 Feb
1:53 a.m.
--- Dave McGuire <mcguire(a)neurotica.com> wrote:
I'd argue that a grant-chain scheme has an advantage over the IRQ
scheme found in Intel hardware - in a PC, you run out of interrupts
pretty quick. In a VAX or PDP-11, you can add devices until you
either run out of convenient vector addresses, or the bus gets too
long to propogate signals reliable (or the AC and DC loading gets
too high).
An example - our 11/750 at work had a TU80 controller, 4 Emulex CS21s
(2 interrupts each) for 64 serial ports (no terminal servers for us!),
3 to 5 COMBOARDs, an RUX50 Unibus RX50 interface, an RL11 RL02 controller,
a DMF32 8-port serial/LPT controller (3 interrupts), a DDCMP interface
for 56Kbps DECnet, and a UDA-50 SDI disk controller (plus three MASSBUS
disk and tape interfaces for our SI9900 controller, the TU78 and our
emergency RM03s). That's 14 Unibus devices in 16 quad-height and hex-
height cards using 19 interrupts. Physically, the cards were in the
internal DD11DK, and in a BA-11 next to the VAX with two DD11DKs - 27
useful slots, if you have some quad-height cards like we did.
Compare that with how many devices you can stuff into a P4, including
built-in I/O.
I am fairly certain that there are only 4 and 9 slot Unibus backplanes. If
there's anything out there that DEC made with more than 9 slots in one
block, part of it is almost certainly where the CPU goes and is not Unibus.
Speaking of CPU and Unibus together, there are a few machines that follow
their own rules - the Unibus slots in a 11/730 and 11/725 (and one model
of PDP-11) are *not* wired identically to the slots in a DD11DK. Our
COMBOARD-I used certain pins for extracting the Unibus signals from the
backplane. It must be heavily modified to fit into one of these Unibuses.
The COMBOARD-II uses the "right" pins and goes into any Unibus without
modification. I don't think there are any DEC cards that have this
limitation, but I wouldn't be surprised if CBD1 wasn't the only 3rd party
card to get it wrong.
-ethan
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On February 1, Gunther Schadow wrote:
Oooh! Must be something sitting on pin B2 - -15VDC.
I read a web article the other day where the guy
describes the
various forms of the Qbus and he also said that you could fry
certain cards when you stick'em in a wrong version of the Qbus.
This is indeed correct...if you plug an RLV11 into a Q/Q backplane
instead of a Q/CD backplane, for example, you'll let out the magic
smoke. Also, why was
the need for grant continuity cards an advantage?
It's not an "advantage" per se...just what the bus needs. SPC slots..."small peripheral controller"
I believe is the correct
expansion of that acronym...you'll want to grab a pdp11 unibus
processor handbook for that info...it's all in there.
Yes.
Are there
UNIBUS backplanes with more than 9 rows?
None that I've seen. I've seen 4- and 9-slot ones. 
2:43 a.m.
Speaking of CPU and Unibus together, there are a few
machines that follow
their own rules - the Unibus slots in a 11/730 and 11/725 (and one model
of PDP-11) are *not* wired identically to the slots in a DD11DK. Our
COMBOARD-I used certain pins for extracting the Unibus signals from the
backplane. It must be heavily modified to fit into one of these Unibuses.
The COMBOARD-II uses the "right" pins and goes into any Unibus without
modification. I don't think there are any DEC cards that have this
limitation, but I wouldn't be surprised if CBD1 wasn't the only 3rd party
card to get it wrong.
-ethan
It's been a long time -- I was trained on the 11/7xx series at DEC in
'85 or so and I don't remember any special things about their Unibus as
far as bus loads, power or signals.
IIRC they 11/730 and 11/725 were pre-cut for DMA devices and had to have
special dual-width Unibus grant cards in place if the slots were empty.
IIRC, again it was because ot the tightness of the packaging of these
slots, anything in the Unibus expansion cabinets was standard.
Bill
--
d|i|g|i|t|a|l had it THEN. Don't you wish you could still buy it now!
bpechter@shell.monmouth.com|pechter@ureach.com
8:59 a.m.
--- Bill Pechter <pechter(a)bg-tc-ppp726.monmouth.com> wrote:
The actual loads were the same. It was that there were two possibilities
for where to get each of the Unibus signals, circa 1981, depending on
exactly what backplane you were looking at. I wasn't at the company
at the time, but the engineer saw one example of the Unibus and based
the board on it. He chose wrong.
Speaking of
CPU and Unibus together, there are a few machines that
follow their own rules - the Unibus slots in a 11/730 and 11/725
(and one model of PDP-11) are *not* wired identically to the slots
in a DD11DK....
It's been a long time -- I was trained on the 11/7xx series at DEC in
'85 or so and I don't remember any special things about their Unibus as
far as bus loads, power or signals. IIRC they 11/730 and 11/725 were pre-cut for DMA
devices and had to have
special dual-width Unibus grant cards in place if the slots were empty.
Yes. We provided instructions for how to cut and replace the NPR
jumper when installing our board because most people didn't have
the dual-height grant cards. We used to ship one with every board.
They cost us $18.75 each (for the model that had no silk-screen
legend, just copper). I don't know what the "Grantasaurus" cards
cost us. Those haven't been made since before 1984.
IIRC, again it was because ot the tightness of the
packaging of these
slots, anything in the Unibus expansion cabinets was standard.
They were a little odd due to the packaging. Speaking of which, when
I said the "11/730", I meant the model that could take the RB80 at the
bottom of the cabinet, the CPU in the middle and the RL02 at the top,
the 11/730-Z. I do not know if they used the same backplane in the
other style of 11/730, the one with the BA-11-style box at the top
of the rack and lots of empty space underneath for cables, etc (like
an 11/24 or 8200). We never had that style, but I kinda always wanted
one because it would have been easier to work on. Wish I still had
my 11/725. :-(
-ethan
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