Subject: PDP-7 - Problems

From: Tore Sinding Bekkedal <[email-masked]>
Date: Fri Jun 6 14:21:42 2003

Hey!

We have two main problems:

1) The RUN button

The RUN button crashes the CPU. So does a RUN invoked by the end of
Paper-Tape End-Of-Tape.

When I stop the CP and CONTINUE, the processor just goes between FETCH and
EXECUTE states on one single instruction.

I made a 9-step JMP program, which I toggled in. I EXAMINEd 0 and
CONTINUEd from 1 which contained a JMP to 0 which jumped to 7, and from
there it went to 70, 700, 707, 770, 777, to 0.

By holding the CONTINUE button, it ran at least 1000 cycles at max speed.

2) IOT Instructions (Input-Output Transfer)

Just plain don't work.

When I READ-IN a Paper-Tape, The Memory Address increments, starting when
the data does. During this process, Memory Buffer = MA.

When the EOT is reached on the Paper-Tape Reader, RUN is invoked (Which
crashes the CP, see section 1)

These are sure signs of communication going on between the CP and the PTR.
Unless, the EOT has some sort of more direct connection.

Not even the Status lights illuminate. They seem to be wired into the IO
rack (which makes sense as most of what it monitors is I/O equipment..
TTY, PTR, PT-Punch etc.

Any help from any DECies greatly appreciated! I have many spares, and if I
don't have the spare in question, I know many who do.

Regards

Tore S Bekkedal

[email-masked]
+47 91 85 95 08 <GMT+1!