More PDP-11 questions - test-drb@ccmp.vtda.org

9 Feb 2009

Tobias Russell <toby at coreware.co.uk> wrote:

...
  Hi,

 Apologies for the constant stream of questions at the moment, I hope I'm
 not consuming too much list bandwidth at the moment. I've brought my
 whole collection out of storage and I'm bringing them all back to
 working condition and going through a steep old learning curve with my
 Unibus machines! 
Fun things to play with... :-)

...
  So here are the latest round of questions:

 1. I have started work on a second 11/05 I have. At the moment it has a
 processor, an 8K core set, NPR cards and a pair of unibus terminators.
 At present when powered up the machine has its run light constantly on,
 shows what looks like a random set of lights on its address/data LEDs
 and doesn't respond on its console.  
What do you mean by "NPR cards"? Technically there is no such thing. 
There is the bus grant cards, and the extended bus grant cards which 
also carry the NPR signal.
The normal bus grant cards only carry BG signals, and thus you normally 
need to connect/disconnect the NPR wire on the backplane.

The symptoms you describe sounds pretty much like an NPR signal problem, 
but of course, it could be a number of different things.

...
  2. I have a Plessy PM1116/B core card. This is a
single slot solution
 consisting of driver/sense logic on a card and a core plane on a
 daughter board. Does anyone have any details/documentation on this card
 or any idea of what slot would be suitable to plug it into (on a 5 1/4"
 11/05-8KW backplane). 
Normally I seem to remember that memory cards can go anywhere. You 
should of course check documentation, as the card can require specific 
voltages only available at certain slots.
I don't have any documentation for that card. Bitsavers perhaps?

...
  3. I have an 11/34A (in 5 1/4" box) which is
experiencing a similar
 constant run light problem to the 11/05. The machine has CPU cards,
 terminators, console card and a MOS memory board in it. With both
 terminators in, run light stays on. If I halt it, the bus error light is
 illuminated.

 If I remove the end terminator and power on, the console is responsive
 and I can deposit values into memory and read them back.

 As with the 11/05 I have connected a scope and checked the power lines
 are supplying the correct voltages without any oscillation. 

 Any ideas? 
Once more: check the NPR signal.

	Johnny

-- 
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