PDP-11/10 repair started

Johnny Billquist bqt at update.uu.se
Mon Oct 5 04:33:19 CDT 2015

On 2015-10-05 07:26, tony duell wrote:
>> You have no memory, and probably no devices to complete the
>> Unibus. So, it is quite likely showing the Unibus is in a
>> jammed state.  At the least, you need a Unibus terminator,
>> and any bus grant cards between the CPU and the terminator
>> (you'd have to check the manual to see how the Unibus is wired.)
> The specific issue of an open grant chain locking the Unibus is a quirk
> of the M9302 terminator (which asserts SACK under such conditions). This
> is unlikely to be a problem on an 11/10.

Why? The 11/10 also have a Unibus, and also needs the terminator as well 
as the SACK and other signals in order.

> But you do need some kind of termination/pullups on the Unibus. At least
> fit the CPU-end terminator (M930 in the right slot near the CPU boards) if
> you haven't done so already.

You most likely want to terminate the other end as well.


Johnny Billquist                  || "I'm on a bus
                                   ||  on a psychedelic trip
email: bqt at softjar.se             ||  Reading murder books
pdp is alive!                     ||  tryin' to stay hip" - B. Idol

More information about the cctalk mailing list