11/45 RTC

[Jay West]

Tony wrote...
> However, I don't see how this can be the cause of the problem. A 180Hz
> signal would still trigger the DL11-W circuit. I doubt the machine would
> get interrupt-bound either.
Nope, standard 110v singlephase outlet. I think something is up with my test 
cable. I'm going to double check it tomorrow. I do know that I set a 
function generator on 50hz and connected my freq counter to it. It 
registered right on 50hz. I moved the freq counter to the /45 and got about 
189hz on CD1. That just seems wrong. I connected my scope to the function 
generator set at the same 50 hz and the scope picked it up sharp at 50hz 
(scope does measurement). I moved it to the /45 and got odd readings, around 
189hz. Here's something else... on the function generator, the 50hz clock 
was square and very clean. It also had a stable display. When looking at the 
trace on the /45, the rise and fall of the square were noticeablely sloped, 
not square. Also, it's like it was triggering right... because the square 
image seemed to alternate between two traces 90 degrees out of phase (1/2 
step back). Made it hard to measure the period.

> Do you have the DL11-W prints (e.g. in an 11/34 printset)? If so, I can
> talk you through some simple tests on the board itself.
I do not have DL11-W prints alas.

Maybe I should start from the beginning and re-explain the problem as I 
percieve it. The machine boots xxdp+ v1.0 and 2.5 just fine. However, when I 
try to boot RT11, the lights flicker and the disk flickers for about 10 
seconds, and then the system just halts. Because of the fact the system can 
read and write full disk packs using VTserver, I kinda doubt there is a 
major read/write problem with the drive. I am GUESSING that what is 
happening is that xxdp does not use interrupts for anything, nor does 
vtserver. My GUESS is that RT11 does, and that there is something wrong with 
interrupts on my machine. I am GUESSING that at some point in the boot 
process of RT11 it tries to use interrupts and thus my machine just dies 
there. I centered on the LTC as a possible route to investigate for two 
reasons - one, I was under the impression that the LTC signal had to be 
present for interrupts to work, and if it wasn't, I'd get this behaviour, 
and two - because when I run the diagnostic program for the DL11-W, it 
specifically complains about the LTC part of the DL11-W with "Bit 7 never 
sets".

Sooooo long story short, I wanted to make sure the LTC and interrupts were 
working, then try rebooting RT11 and see if that was the issue. Bear in mind 
I have three DL11-W cards. I guess it's possible, but I find it hard to 
believe they are all bad (although they do fail the diagnostic in different 
ways). I've also tried several different RL11 controllers, and I've triple 
checked the NPG jumpers and grant cards. Maybe I should be looking in a 
different direction. I am going to go back and run the trap and interrupt 
tests tomorrow, I believe the machine fails the interrupt test.

Jay