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From: KENNER@NYU-CMCL1.ARPA (Richard Kenner)
Newsgroups: mod.computers.vax
Subject: +5V power on 11/750's
Message-ID: <3452F4BF4.1214002C;1985@CMCL1.NYU.ARPA>
Date: Wed, 11-Dec-85 07:36:00 EST
Article-I.D.: CMCL1.3452F4BF4.1214002C;1985
Posted: Wed Dec 11 07:36:00 1985
Date-Received: Fri, 13-Dec-85 02:10:54 EST
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Approved: info-vax@sri-kl.arpa

It is certainly true that a standard BA11-K has two 32A power supplies for +5V
(one for SU #1 and #2 and the other for SU #3-5 -- this is why you can't put a
DD11-DK at positions 2-3) and that some (very) old BA11-K's have 25A supplies.

However, I thought that the original question was what is the available +5V
UNIBUS power for 11/750's.  Here the question is more complicated because there
isn't a separate supply for the UNIBUS.  I think there may be only one +5
suppy for the whole machine but the UNIBUS certainly shares power with
things like the UNIBUS adapter, MASSBUS adapter, DR750, etc.

A while ago DEC "increased" the amount of UNIBUS +5 power available. They did
this by declaring that most sites don't use a DR750 so the power reserved for
it could be used for UNIBUS devices.  You can also trade off against the
RH750 power if you don't have a MASSBUS but the standard DEC configuration
rules don't cover this case.

This information is rather old so things might have changed in the last few
years but I sort of doubt it.  Unfortunately, I don't remember the exact
numbers.  They may well amount to the "standard" 25/32A but, if they do, it's
for a different reason.

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