Argh!!! PDP-8/m Memory

From: Chuck McManis <>
Date: Sat Nov 20 23:20:57 1999

Try this:
         Set all switches to 0, Halt is down, key is set to power ON,
rotary switch to MD.
         Press CLEAR
         Press Extd Addr Load
         Set the switches to 200 octal
         Press Addr Load.
         Now flip the switches back to 0
         press Deposit
         set the switches to 1
         press deposit
         set the switches to 2
         press deposit
         ... repeat until you get to 10 octal...
         Now set the switches to 0200 octal
         press ADDR LOAD
         press EXAMINE
         Data LEDs should show 0
         press EXAMINE
         Data LEDs should show 1

If they do, you are reading back memory and writing it. If they don't you
have a problem.

The first thing to check is that all the top connectors are in fact on.
There should be no "edge" connectors visibla at the top.

The next thing to check is the first board in the MEMORY stack has three
solder jumpers in the lower right hand corner. They should _all_ be
soldered in. (that's three 0's or page 0)

The next thing you should check is that the back plane does _not_ have gunk
in it. This is a very common fault on old 8's.


At 08:33 PM 11/20/99 -0800, you wrote:
>Well, with the aid of the "PDP-8/e Simulator" for the Mac, I figured out
>how to use the front panel, and execute the "Initial Operating Check".
>Load it into the real PDP-8/m, and start it. Wait a minute, that's not
>what it's supposed to be doing...
>After a bunch of investigating, and going back to the "PDP-8/e Simulator"
>to figure out how to display the contents of memory, I discover that there
>is nothing in memory :^(
>Based on the fact I can see what I'm trying to enter when I've got the
>switch set to 'MD' and hit Deposit, it sounds to me, suspiciously like I've
>got a bad 4K Core set.
>Anyone have any suggestions on something to check?
> Zane
>| Zane H. Healy | UNIX Systems Adminstrator |
>| (primary) | Linux Enthusiast |
>| (alternate) | Classic Computer Collector |
>| Empire of the Petal Throne and Traveller Role Playing, |
>| and Zane's Computer Museum. |
>| |
Received on Sat Nov 20 1999 - 23:20:57 GMT

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