PDP-11/10 repair started

william degnan billdegnan at gmail.com
Mon Oct 5 13:59:07 CDT 2015

What are the DC LO and AC LO values off the backplane?  Do they change when
you insert the CPU card.  (one at a time).

On Mon, Oct 5, 2015 at 12:01 PM, Johnny Billquist <bqt at update.uu.se> wrote:

> On 2015-10-05 17:56, Henk Gooijen wrote:
>> -----Oorspronkelijk bericht----- From: Johnny Billquist Sent: Monday,
>> October 05, 2015 5:44 PM To: cctalk at classiccmp.org Subject: Re:
>> PDP-11/10 repair started
>> Ok. I got the initial impression that you only had the CPU in. Thanks
>> for the expanded info.
>> When you don't have any core memory, I wonder if you might need bus
>> grants in those slots as well...? It's not as if they aren't a part of
>> the Unibus... Memory sits on the Unibus, just like everything else,
>> remember? Needs to check further if any special wiring are in place for
>> those slots, though.
>> Johnny
>> =========
>> I am not sure the "core slots" would need grant cards. The documentation
>> is clear about slot 3-4-5 as SPC, needing grant cards. I never saw any
>> doc where the core memory slots, when optional, but not installed, could
>> be used as an SPC slot. I certainly am Not "trying" that ...
>> I did try the system *with* the core slots filled with the correct boards
>> but the behavior remained the same.
>> To make fault finding not more complex, I removed the core board set.
> Ok. Not sure if it makes it more complex or not, but I guess it's not the
> issue right now anyway.
> But my original comment about the behavior you described being very much
> like what I've seen on other machines with bad/no termination still
> applies. CPU seemingly stuck, but doing a master reset sortof gets it out.
> But not functioning as it should.
> Well, no more ideas here at the moment.
>         Johnny


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