Q?: BA23 type for PDP-11/93

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Darkstar

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Jan 30, 2010, 5:23:27 AM1/30/10
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Oh Wizards Of DEC,

Someone has asked me for a BA23 Backplane/Chassis
to rebuild a PDP-11/93 from a pile of boards.

I never acquired a PDP-11/93 so I was going to build
something out of a PDP-11/23 or PDP-11/73 chassis.
(I have an "elephant ears" cabinet but I can't get to it.)

Now the PDP-11/93 should be 22 bit addressing.
I can't remember any BA23s that had 18 bit addressing.
I think the first three slots were Q22/CD and the rest
were double Q22.

What sort of Connector Panel was required for the
console/second Serial Unit?
Wasn't there a fix for the internal Power Cabling?
Didn't the memory go in front of the processor card?

I'll have to get a list of cards for extra Connector Panels.

Thanks in Advance, Andy.

Bruce Cook

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Jan 30, 2010, 7:13:36 PM1/30/10
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Darkstar wrote:

> Now the PDP-11/93 should be 22 bit addressing.
> I can't remember any BA23s that had 18 bit addressing.
> I think the first three slots were Q22/CD and the rest
> were double Q22.

IIRC, the 11/23 was "officially" an 18 bit system. I don't remember if the
backplanes came out that way, however I do remember hacking additional
address lines into some backplanes (may have been 3rd party) to make 11/23s
22 bit. ( The processor card actually had 22 bit support, the backplane
didn't).

Bruce

John Wallace

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Feb 1, 2010, 4:09:13 PM2/1/10
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On Jan 30, 10:23 am, Darkstar <nos...@example.net> wrote:
> Oh Wizards Of DEC,
>
> Someone has asked me for a BA23 Backplane/Chassis
> to rebuild a PDP-11/93 from a pile of boards.
>
> I never acquired a PDP-11/93 so I was going to build
> something out of a PDP-11/23 or PDP-11/73 chassis.
> (I have an "elephant ears" cabinet but I can't get to it.)
>
> Now the PDP-11/93 should be 22 bit addressing.
> I can't remember any BA23s that had 18 bit addressing.
> I think the first three slots were Q22/CD and the rest
> were double Q22.

That's what I remember too, but it's been a while. More info at e.g.
http://hampage.hu/dr/ba23.html

>
> What sort of Connector Panel was required for the
> console/second Serial Unit?

Don't remember :(

> Wasn't there a fix for the internal Power Cabling?

Yes, mentioned (very briefly) on webpage above.


> Didn't the memory go in front of the processor card?
>

Yes, standard PMI practice.

> I'll have to get a list of cards for extra Connector Panels.
>

Most stuff will work without the connector panels, but you may have
EMC/airflow/other issues (unlikely though) or occasionally issues with
connector types/genders and things.

> Thanks in Advance, Andy.

Good luck.

Run.PDP

unread,
Mar 11, 2010, 12:34:45 PM3/11/10
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On Feb 1, 10:09 pm, John Wallace <johnwalla...@yahoo.co.uk> wrote:
> On Jan 30, 10:23 am, Darkstar <nos...@example.net> wrote:
>
> > Oh Wizards Of DEC,
>
> > Someone has asked me for a BA23 Backplane/Chassis
> > to rebuild a PDP-11/93 from a pile of boards.
>
> > I never acquired a PDP-11/93 so I was going to build
> > something out of a PDP-11/23 or PDP-11/73 chassis.
> > (I have an "elephant ears" cabinet but I can't get to it.)
>
> > Now the PDP-11/93 should be 22 bit addressing.
> > I can't remember any BA23s that had 18 bit addressing.
> > I think the first three slots were Q22/CD and the rest
> > were double Q22.
>
> That's what I remember too, but it's been a while. More info at e.g.http://hampage.hu/dr/ba23.html

>
>
>
> > What sort of Connector Panel was required for the
> > console/second Serial Unit?
>
> Don't remember :(
>
> > Wasn't there a fix for the internal Power Cabling?
>
> Yes, mentioned (very briefly) on webpage above.
>
> > Didn't the memory go in front of the processor card?
>
> Yes, standard PMI practice.
>
> > I'll have to get a list of cards for extra Connector Panels.
>
> Most stuff will work without the connector panels, but you may have
> EMC/airflow/other issues (unlikely though) or occasionally issues with
> connector types/genders and things.
>
> > Thanks in Advance, Andy.
>
> Good luck.

Correction on the memory:

The 11/93 CPU is a complete "all inclusive" single board computer,
with full 4M or slightly cheaper 2M memory at full CPU speed included
on the CPU board, besides 8 serial lines and bus-interface.

No external memory can be connected to this one (outside the I/O-
area), and why should it?

If your card "only" has 2 MByte, there are 4+2 circuits missing at the
right edge of your card (when viewed with the bus-connectors close to
you body). Get your hands on these devices (not easy, not impossible)
- you need the same types as are allready sitting there with 4 + 2
config, and (have them) soldered. Please note that the soldering is
not trivial, as the 4 devices are "surface mounted" with the legs
beeing placed under the circuit...

While working on the card, do get an upgrade for the firmware to rev.
2.x The older 1.06 will not fix dates after Jan-1 2010. The 27C512
quite left quite close to the bus has this code inside.

There is a special "Back-plate" with one DB-25, 7 times DB-9, one 2-
digit red display and one dip-switch (8 positions). The module is
"double", ie it consumes 2 of the 4 slots in the rear of the BA-23
chassies. 2 flat-cables connect this module with the CPU-board. I can
find out the DEC-number if requested.

The emulated SLU:s are DL-11, but with a 5 level SILO. If you intend
to do any serious serial communications, please try to find a better
interface, not to overload the CPU with DL-11-interrupts!

Good luck with the 11/93
/Göran

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