Subject: PDP-11/35 FC?

From: Joe <[email-masked]>
Date: Fri Mar 28 13:56:00 2003

First, what's the significance of the FC on the model number?

  Second, I went through chassis and here's a list of the cards in it. QED stands for Quickware Engineering & Designs. They made several of the cards in this one. Anyone have any info on them? H,Q,U stand for Hex-bus, Quad-bus and Uni-bus respectively.  Anyone want to take a stab at id'ing these cards?

    Slot:  Card:
	4	M7231D H Data Path
	7	CI M60 made by QED Q
	9	90 CPU made by QED has DCJ11-AA IC  Q
	11	MS 95 made by QED  H
	15-16	M920 U
	19-20 	M920 U
	16	M7254 Q
	17	M7255 Q
	18	M7256 Q
	19	M7257 Q
	22	M7762 H
	23	Tektronix CL3 Date/Time Option Q
	24	Datasystems DLP-11 Q  Printer card?
	27	M7228 Q
	29	M7800 Q
	31	M7800 Q
	33	M7800 Q
	36	M7911 Q
	37	M7912 H
	38	M7821 fits in single slot (#2)
	38	M105 fits in single slot (#3)
	38	M796 fits in single slot (#4)
	38	M930 U bus terminator?  installed in bottom two slots 
	39	M795 installed u[pside down. Is this correct?

   Joe

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From: Ethan Dicks <[email-masked]>
Date: Fri Mar 28 14:26:00 2003

>   First, what's the significance of the FC on the model number?

No idea.  If this were "Suspended", I'd guess "Filter Computer" :-)

>   Second, I went through chassis and here's a list of the cards in it.

> 	9	90 CPU made by QED has DCJ11-AA IC  Q

Neat - plenty of horsepower there!

> 	19-20 	M920 U

Jumper cards.  Interesting comment about them here:

http://www.varx.com/va01005.html

I think they mean that in modern Unibus designs, the cable length
is suboptimal to prevent signal reflection.  The newer jumper blocks
are taller with more mylar cable folded up inside.  Consult DEC's
Unibus Handbook for details on Unibus configuration.  I figure if
the machine has them now, they'll be OK, but if all you want to do
is hook some DD11CKs and DD11DKs together, go with the newer ones.

> 	19	M7257 Q

RK11D (including the backplane)

> 	22	M7762 H

RL11 (RL01/RL02 controller - up to 4 drives)

> 	27	M7228 Q

KW11-P real-time clock.

> 	33	M7800 Q

DL-11E serial boards

> 	39	M795 installed u[pside down. Is this correct?

TS03 controller (the entire backplane - these aren't SPC (Small Peripheral
Controller) slots).  Not sure about the M795 being upside-down.  I'd
check that before applying power.  Sometimes non-DEC goobs aren't paying
attention when they randomly pull boards.

-ethan

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From: Joe <[email-masked]>
Date: Fri Mar 28 15:03:38 2003

>No idea.  If this were "Suspended", I'd guess "Filter Computer" :-)

    I wondered if it had anything to do with the front panel.

>Neat - plenty of horsepower there!

   If you say so. Can you tell me more?

>Jumper cards. 

   What do they do, jumper the CPU section to memory section?

 Interesting comment about them here:
>> 	36	M7911 Q   TMB11 TAPE CONTROL 1 
>> 	37	M7912 H   TMB11 TAPE CONTROL 1 Hex

   I looked these two up and it looks like they're both tape controllers. Is that right? Why TWO controllers? There was both a PT reader/punch and mag tape drive on the system is that why it has two controllers? (Does each controller only handle one device?)

>> 	38	M7821 fits in single slot (#2)  SINGLE HEIGHT INTERRUPT CONTROL BD 
>> 	38	M796 fits in single slot (#4)  SINGLE HEIGHT UNIBUS MASTER CONTROL BD 
>Controller) slots). 

   What's a TS-03 controller?

 Not sure about the M795 being upside-down.  I'd
>attention when they randomly pull boards.

    That's what I thought but I thought I'd ask the experts.

    Joe

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From: Ethan Dicks <[email-masked]>
Date: Fri Mar 28 15:26:00 2003

>    If you say so. Can you tell me more?

It has a 3rd-party CPU board with the same chip as the 11/73
through 11/93.  I don't know the particular clock speed of
any QED products, but you are looking at a box that is at least
as powerful as a MicroPDP-11/73, and perhaps as powerful as
a PDP-11/93 (the "90" is suggestive but not definitive).
 
>    What do they do, jumper the CPU section to memory section?

They pass the Unibus across from backplane to backplane.  If you
look underneath, you'll see there is no connection from section to
section.  Each of those backplanes can be removed.  Unlike a PeeCee,
DEC stuff was modular, even in the CPU cabinet.  After you left the
CPU backplane, things started getting optional.

>    I looked these two up and it looks like they're both tape controllers.
> Is that right? Why TWO controllers?

It's not two controllers.  It's two parts of *one* controller.

> There was both a PT reader/punch and
> mag tape drive on the system is that why it has two controllers? (Does
> each controller only handle one device?)

No.  These boards are both part of the same device.  The PC05 controller
is somewhere else (didn't see it in your list).  It will be a single
quad card with two 40-pin Berg connectors, IIRC.

> >TS03 controller (the entire backplane - these aren't SPC (Small
> Peripheral Controller) slots). 
> 

A controller for a TS03 (or similar) magtape drive.  DEC nomenclature
"T" for tape, "TS" for one kind of register set (as opposed to "TM",
which looks different to the CPU and uses different boot code and device
drivers), "03" for a particular model of tape drive.  The TS03 was 800 bpi
(only?) and took small reels.  It didn't even have a takeup reel - the
tape packed on itself on a bare aluminum hub to save space - the entire
tape drive was about the size of a toaster oven (19" wide, 10.5" tall
and less than 24" deep).  I expect that the controller could be used
with other tape drives, but I haven't personally seen that.

This entire backplane and all the cards I grouped together is the tape
controller.  You can't remove part of it and migrate it around, nor can
you put other boards in this backplane and expect them to work.

Unlike "modern" machines, just because the slots look identical from the
top doesn't mean they _are_ identical.

A slot that can take a single-card controller is called a "Small Peripheral
Controller" slot (SPC) - it defines where to find what Unibus signals on
what pins.  The alternative is a device that has a backplane that is Unibus
on the front and back (where the M920s, et al. go), but "random" in
between.  Cards like the M105 and the M796 are standard components in a
Unibus controller of this vintage.  Cards like the M7911 and M7912 are
what make it a TS03 controller as opposed to an RH-11, for example.

The M930 in the middle there is another common thing of that era - they
used Unibus cables to get the tape drive signals from the controller
backplane to the tape drive.  There are a pair of H851s at the edge of
the board in the TS03 drive to receive that cable.  The RK05 uses a 
similar scheme - Unibus cables, but *not* Unibus signals.  As long as
the Field Engineer can keep them straight (not typically a problem),
it's a good thing to reuse parts like that - keeps costs low and makes
spares kits easier to stock.

You have a mix of ancient and modern there (ancient being 1970-1978;
modern being 1984-present).  Not unusual in a machine that was bought
many years ago and operated continuously since the present.  Much like
doing archaeology of an ancient city that's still occupied, it can
cause confusion in the uninitated.  I've never seen a machine quite
like this, but no single part of it is terribly unusual.

-ethan

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From: Joe <[email-masked]>
Date: Fri Mar 28 21:20:35 2003

>It's not two controllers.  It's two parts of *one* controller.

   OK then why are both "Control 1"?  They both sound like the first card of a set.

    Joe

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From: Ethan Dicks <[email-masked]>
Date: Fri Mar 28 22:56:01 2003

> >> >> 	37	M7912 H   TMB11 TAPE CONTROL 1 Hex
.
.
.
>    OK then why are both "Control 1"?  They both sound like the first card

I have absolutely no idea.

-ethan