11/45 progress

From: Eric Smith <eric_at_brouhaha.com>
Date: Wed Feb 16 02:24:57 2005

Jay wrote about the PDP-11/44:
> I know the cpu backplane includes a tiny number of unibus
> slots.

Yes, they're at the ends of the backplane. The only thing Unibus slots
are normally used for are cables or jumpers to other backplanes, or
terminators (sometimes w/ bootstrap).

What you're probably thinking of are SPC (Small Peripheral Controller)
slots. Those are what single-board options plug into. A quad SPC
module plugs into the C-F positions. A hex SPC plugs into A-F (obviously).
Many (but not all) hex SPC slots other than the ones at the very ends
of backplanes have modified Unibus wiring on the A-B positions, for MUDs
(Modified Unibus Devices).

> I'll be damned if I can find docs that show exactly which slots (I
> know they are at the end)...

It's in either the 11/45 maintenance manual or the KB11-A maintenance
manual. I think both have it, actually. I was just looking at those

> I'm still going through it, but no obvious hints so far.

All right, you made me get out the manuals. EK-11045-MM-007 page 5-7.
You can use three quad-height SPC modules in slots 26-28.

> Still trying to find out how I determine if the memory in my /34 will work
> in my 45. It is plugged into... I think it's the 3rd slot on the /34. Non
> DEC memory. That slot is labled SPC/MUD.

Not in the 11/45 CPU backplane, as it has no MUD slots. You need a
DD11-CK (4 slot) or DD11-DK (9 slot) backplane, which provide 2 or 7
MUD/SPC slots, respectively.

> So what is SPC/MUD in relation to Unibus, hum?

I don't think it had been invented yet when the 11/45 was introduced.
Try the 11/34 documentation or 11/44 documentation.

> The term "modified unibus" doesn't mean a whole lot to me. I
> hear some /34 memory will work in the /45, some wont... unless you build a
> custom backplane or something (I think to get MUD slots)?

Any memory that works in an 11/34 should work fine on an 11/45, provided
that you add a backplane with MUD/SPC slots.

> So just which manual do I go to for this kind of info?

Ideally the tech manual for the memory.
Received on Wed Feb 16 2005 - 02:24:57 GMT

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