2 Nov
2010
2 Nov
'10
10:30 a.m.
-----Original Message-----
From: cctalk-bounces at classiccmp.org [mailto:cctalk-
bounces at classiccmp.org] On Behalf Of Chris Elmquist
Sent: Monday, November 01, 2010 8:30 AM
To: Classic Computer Talk; Classic Computer Tech
Subject: PDP-11/34A bring up
I am the new keeper of the PDP-11/34A that Jack Rubin rescued a while
ago and wrote about here,
http://decpicted.blogspot.com/2010/01/pdp-1134a-data-systems-design-
dsd-880.html
I took it on a road trip from Chicago back to St. Paul after VCFMW
in September.
Congratulations! The 11/34 is a good mid-size machine. I run UNIX 6th Ed. on mine.
I've been doing a lot of cleanup on it and finally got to the point
where I could power it on (just the CPU box) this weekend.
I think now I need to learn about Grant Continuity ;-)
There is a M9302 terminator installed in the last slot (left most when
looking from the front of the machine) and also an M9312 in slot 4
(amoungst the CPU and cache cards).
Two of the original boards are removed from the backplane... the DSD
808830 controller and the DILOG DU130 tape controller. They were in
slots 12 and 13.
I then also have an RL11 on hand but it is not currently installed in
the machine.
When I power up the machine, it immediately lights the RUN light on the
KY11-B programmer's console. No matter what I do from that console, I
cannot get it to exit RUN or print anything to the serial terminal.
However, if I remove the M9302 terminator (a trick I found on some web
page), then sure enough, I can HALT it, the RUN light goes out and I
can
do CTRL+BOOT and the serial terminal will spring to life with a
register
dump and the '@' prompt.
I'm pretty sure that my problem is the empty slots 12 and 13 where
boards
used to be and should now have Grant Continuity cards installed
instead...
but I am curious why pulling the M9302 makes it "work". What is the
mechanism at play there?
I also suspect that I may have to look at the backplane wiring for
slots
12 and 13 to put back whatever DMA jumpering might have been modified
for
the two cards that used to be there-- or, at least for one of them as
I can probably put the RL11 into one of those slots and it requires
DMA.
I agree that it's probably the grant continuity problem that's tripping you up -
although I'm not sure why removing the far terminator gives you at least partial
functionality. But whatever.... It's almost certain that both of those cards use
DMA.
There are two grant lines to worry about: there is the Bus Grant line for
processor-mediated transfers and the Non-Processor Grant (NPG) line for what we now call
DMA. There are two types of continuity cards: the G727 that passes the BG signal and the
G7272, which passes both the BG and NPG signal. The larger card isn't as easy to
find, but you can also rejumper CA1 to CB1 on the backplane and then use a G727. -- Ian
UNIX is user friendly. It's just selective about who its friends are.
Ian S. King, Sr. Vintage Systems Engineer
Living Computer Museum
A project of Vulcan, Inc.
http://www.livingcomputermuseum.org