jcwren wrote:
> And I still want a system that will support a front panel, in the end.
If you want a PDP-11 with a "real" front panel (binary switches and lights),
the choices are:
PDP-11/05 (or OEM model, PDP-11/10) Small (CPU on two hex
modules). Relatively slow.
PDP-11/20 The original. Sometimes simply marked "PDP-11". The
only PDP-11 that isn't microcoded. Lots of small
cards.
PDP-11/40 (or OEM model, PDP-11/35) Mid-range.
PDP-11/45 (or OEM model, PDP-11/50) High end. Fast.
PDP-11/55 Same CPU as 11/45, but with bipolar RAM. Very fast.
PDP-11/70 PDP-11/45 CPU extended to support 22-bit addressing,
32-bit memory bus, cache, and Massbus peripherals.
Very very fast (depending on cache hit ratio).
If you will settle for the "calculator-style" front panel (octal keypad
and LED display), there are three more choices:
PDP-11/04 Low end, replacement for 11/05.
PDP-11/34 Mid-range, replacment for 11/40.
PDP-11/60 High end of mid-range. More microcode than any
other non-VLSI PDP-11 model; only TTL-based PDP-11
that supported user-written microcde. If it had
had 22-bit addressing, it might have been popular.
The PDP-11/44 was the last of the TTL-based PDP-11 processors, but it used
a microprocessor-based console, so there are no switches and blinkenlights.
> is there a resource anywhere of what parts will play together, and makes
> for a sensible workable system?
These systems were not all marketed concurrently, since they were
designed at different times over more than a decade, so there isn't any
single place where they are all described in detail.
The information on supported configurations was found in the "PDP-11
Systems and Options Catalog", and in Software Product Descriptions (SPDs).
Those are hard to find now, but the various PDP-11 Processor Handbooks and
Peripheral Handbooks are easier to find and turn up on eBay from time to
time. Some of the processor and system reference manuals are on
www.bitsavers.org.
I'll ignore Qbus for the remainder of this posting, because the
PDP-11 models that have "real" front panels don't have Qbus. Normally
Qbus is only found on some (but not all) of the VLSI-based PDP-11s,
using the LSI-11, F-11, T-11, or J-11 chip sets. Able sold a "Qniverter"
product that allowed the use of Qbus peripherals on a Unibus system, or
vice versa, but these are not common.
PDP-11 peripherals (and some of the memory) come in two main types,
Unibus System Units and Small Peripheral Controllers (SPC). A System
Unit is a collection of cards in a specially-wired 4-slot or 9-slot
backplane. Be careful when buying modules that go in System Units; if
you don't have the backplane, they're of no use. Examples of System
Units are the RK11-D DECdisk control, RH11 Massbus adapter, and
MM11-L core memory.
SPCs are peripherals on a single quad or hex module. They need to go
in an SPC slot in a backplane. The system or processor reference
manuals explain which slots in the processor backplane are wired for
SPCs. The DD11-CK and DD11-DK are 4-slot and 9-slot generic SPC
backplanes, so if you don't have extra SPC slots in your processor
backplane, you can use on of these. Also, so dedicated System Units
have a few extra slots that can accept SPC modules.
You have to be VERY careful about what slots you plug things into;
slots for dedicated cards, SPC modules, Modified Unibus devices, etc.
all physically look identical, but if you plug things into the wrong
kind of slot, at best they don't work and damage to either the module
or the system is possible. ALWAYS check the reference manuals if you
aren't sure (and best to check even if you think you know it; From
personal experience I can state that it's very easy to be wrong about
these things).
As a general rule, the Unibus is present on the A and B edges of the first
and last slot of each backplane. (Only the last slot on some processor
backplanes.) When you have multiple backplanes in one box, you connect
them via M920 or M9202 jumpers. M920 are the short ones. M9202 are tall,
and have a folded flat cable packed between the two connector modules.
The M9202 is used to distribute the AC loading of the bus better.
To connect backplanes between separate cabinets, you need BC11 cables.
A few early peripherals, such as the TC11 DECtape control and RK11-C
DECdisk control, have one or more 19" mounting panels full of modules.
For these you have to check the docs to find out which backplane slots
are for the Unibus In and Unibus Out cables.
The Unibus-out slot of the last backplane *MUST* have a terminator.
The M930 was at one time common, and is a really small card that's
hard to get out of a full backplane. The M9302 is a tall card, and
IIRC does a bit more than the M930. On more recent systems, the
M9301 and M9312 are common, and combine the terminator with bootstrap
PROMs.
SPC modules use signals on the C, D, E, and F edges. SPC modules
come in quad and hex height. Hex height SPC cards normally do not
use anything from the A and B edges other than power.
The A and B edges of slots intended for SPC cards sometimes are
wired for Modified Unibus Devices (MUDs). Be careful not to plug
a MUD device into a standard Unibus slot or vice versa. The only
MUD devices I know about are memory cards, but perhaps there are
others.
There are also "Extended Unibus" slots in the PDP-11/24 and PDP-11/44,
which have extra memory address lines. Once again, be very careful
how you use those slots.
Since all of the PDP-11 systems with "real" front panels used Unibus,
you can generally use almost any Unibus or SPC peripherals on any of
the CPUs. Memory is a little bit trickier; the high-end CPUs like the
11/45 and 11/70 require special memory. The 11/20 uses Unibus memory,
but it uses different backplanes and power harnesses than anything else,
so most of the Unibus core memory System Units cannot be used in the
11/20 chassis, though they will work fine with the 11/20 if installed
in an expander.
Hopefully this has given you some idea of what you're getting into.
It probably sounds complicated, and I've deliberately emphasized some
of the areas in which you can get into trouble, but it's really not
that bad as long as you read the documentation. When in doubt, ask
here or over in alt.sys.pdp11.
Eric Smith
[ClassicCmp posting copyright 2003 Eric Smith. Not to be redistributed
without permission of the author.]
Received on Wed Dec 17 2003 - 03:05:20 GMT
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