Even more PDP-8/A weirdness (was: Re: PDP-8 diagnostics SR settings?)

Johnny Billquist bqt at update.uu.se
Sat Sep 12 11:48:41 CDT 2015

On 2015-09-12 17:23, Charles wrote:
> Since the computer doesn't mind doing boring, repetitive tasks, I set
> the 11/23+ to yet again remaking the bootable RL02 pack (3 hrs at 9600
> baud while I did other things).
> Plunked it in (without the programmer's panel connected), hit the boot
> switch on the limited function panel, and it fired right up to the "."
> prompt.
> Did a directory of the free space which printed, set the date to 11 Sep
> 75, and had a phone call for a while.
> Back to the console, entered R BUILD (just to do the PR, not save it)
> and system halts. Reboot - back to the same crap of fault light flashes
> on the drives, no boot. Sigh.


Well. This is definitely good progress. We can rule out the RL8A, and I 
think it has never been the problem.

So, either something is corrupting the bus, or the memory is bad.

Correct me if I'm wrong, but if I got this right, you wrote the boot 
code by hand into memory, single-stepped it, and after a while, you had 
bad contents in memory.

Now, execution here would only be reading from memory, and not writing 
to it. Furthermore, this is MOS, so it does not get rewritten on reads.
That would, to me, suggest that the memory board is the problem.
Do you have any other memory board around?


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