Image Map Image Map
Results 1 to 6 of 6

Thread: pdp8 MAINDEC Memory Test Results

  1. #1

    Default pdp8 MAINDEC Memory Test Results

    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?

  2. #2
    Join Date
    Aug 2010
    Location
    Silicon Valley USA
    Posts
    803
    Blog Entries
    4

    Default

    Quote Originally Posted by NicolasF View Post
    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?
    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

  3. #3

    Default

    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!

  4. #4
    Join Date
    Jul 2014
    Location
    Rhode Island
    Posts
    1,214

    Default

    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.
    Member of the Rhode Island Computer Museum
    http://www.ricomputermuseum.org

  5. #5
    Join Date
    Jun 2012
    Location
    UK - Worcester
    Posts
    3,128

    Default

    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

  6. #6
    Join Date
    Jul 2014
    Location
    Rhode Island
    Posts
    1,214

    Default

    The MEMORY ADDRESS test is supplied in RIM format and uses a very limited set of instructions.
    Member of the Rhode Island Computer Museum
    http://www.ricomputermuseum.org

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •