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pdp8 MAINDEC Memory Test Results

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NicolasF

Experienced Member
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Jun 28, 2006
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Argentina
Hi,

I'm trying to run MAINDEC-8E-D1AA-D on a pdp8. It seems like the upper core test is successfull but the lower one fails.
Here is a video of the upper test:

https://youtu.be/y5M5JD5Q9V4

I get a single character after 5 minutes on the upper test, but not the number 5 character as the manual says, maybe I have a baud rate issue.

And the lower test:

https://youtu.be/8YZgkaxyfoA

This test seems to hang as soon as it starts. I can't figure out how to read the results of the rest, seems like the manual is not very clear about this.
Any ideas?
 
NicolasF said:
Hi,

I'm trying to run MAINDEC-8E-D1AA-D on a pdp8. It seems like the upper core test is successfull but the lower one fails.
Here is a video of the upper test:

https://youtu.be/y5M5JD5Q9V4

I get a single character after 5 minutes on the upper test, but not the number 5 character as the manual says, maybe I have a baud rate issue.

And the lower test:

https://youtu.be/8YZgkaxyfoA

This test seems to hang as soon as it starts. I can't figure out how to read the results of the rest, seems like the manual is not very clear about this.
Any ideas?
Click to expand...

That is the old version that is really just designed to test a basic 4KW system.

Why not use this instead: MAINDEC-08-DHKMA-A
which requires a minimum of 8KW (two fields) up thru 32KW (eight fields).
This is what I use to test my 16KW PDP-8m (and my 32KW PDP-8fpga).

After loading, this is what you would see:
Code: 
PDP-8E EXT MEM DATA & CHKBD

SETUP SR & CONT
  <<<HALTed; set SR & hit continue>>>

4 FIELDS IN THIS SYSTEM
FIELDS SEL'D ARE 3 2 1 0
PROG WILL RELOCATE
5
5
5
5
5
5
5
5
5

In my case I set SR=0003 since my 8m has only 16KW (four fields, 0-3).

Don

PS: You can get the diagnostic here (BIN, RIM, PDF, etc): https://www.ak6dn.com/PDP-8/MAINDEC/MM8-EJ_memory/ if need be
 
Ok, I have some questions:

1- On the "Preliminary programs" of the manual it says "ALL DIAGNOSTICS FOR A BASIC 4K PDP-8E MUST HAVE BEEN PREVIOUSLY RUN SUCCESSFULLY" but I haven't succesfully run them. Should I try this test anyway?
2- On the "Operating Procedure - To start a program" it says "A. SET THE SR TO IF AND DF OF THE FIELD THAT CONTAINS THE PROGRAM." What are IF and DF?
3- My pdp8 only has 2 memory fields 0 and 1. So I'm guessing I should set the Switch Register to 0001, am I right?

Thanks!
 
2, IF is Instruction Field and DF is Data Field.
3, If you loaded the MAINDEC into memory field 1, then you would set the Switch Register to 1.
3, If you loaded the MAINDEC into memory field 0, then you would set the Switch Register to 0.
 
Question 1 - answer 'maybe'...

If you suspect a memory problem - answer: NO, go with the memory test.

If you don't know the state of the machine - answer: YES.

The memory test program uses CPU instructions. If there is something wrong with a CPU instruction, you will either get false positives from the memory test - or (even worse) false negatives (i.e. a memory fault may not show up).

What you should do is to start off with the low-level MAINDECS and work your way up to the memory tests.

Dave
 
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