Odd Symptom PDP 8e Running Programs

Bill Degnan billdegnan at gmail.com
Sun Dec 15 11:10:01 CST 2019

Hi - I am looking for some help.

I have had a PDP 8e with RK05 drives that has run pretty reliably for many
years, but after moving it a strange symptom has come up, preventing it
from operating correctly.  I am hoping someone can advise.

Here is an example

1.  Power up drives and PDP 8e
2.  Load OS/8
3.  Load ADVENT
4. Program loads, asks if I want instructions.  I can enter Y or N and the
system responds.  The familiar scrolling light pattern appears on the front
panel to indicate awaiting input
5.  As soon as I attempt an action such as "S" (with no quotes) the front
panel freezes and I have to CTRL+C to exit ADVENT, dumping me to the dot

Similar issue when running the MUSIC.SV program. I can load the program and
get up to the point of entering a song, but when I enter a song name the
system freezes on the first note.

BASIC works fine however.  Which tells me that I have a CPU problem, not a
RAM problem but this is just my hunch.

Any ideas how to diagnose this?  Running MAINDEC programs is always
frustrating. I am attempting to load the main DECX8 SYSTEM EXERCISER to see
if there are any clues from this as to the cause of the freezing system.



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