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Thread: Memory Card Issues

  1. #1
    Join Date
    Apr 2017
    Location
    Switzerland
    Posts
    224

    Default Memory Card Issues

    Hi,

    I'm looking for a small memory test program that can be run on a PDP-11 standalone. I have built a 2Mbyte SRAM Q-Bus card but something is wrong. I have some simple memory tests which all show no error. But when I try to boot RSX-11M-Plus, which works perfectly with the other memory which is a 1Mbyte card, on the same system it crashes. I admit that I never had more than 1Mbyte on the system before, but I cannot imagine that the memory size itself is a problem, so it must be something with my SRAM card.

    Code:
    $DLˇ
    
    SYSTEM FAULT DETECTED AT PC=055504  FACILITY=000300  ERROR CODE=000100
    
    CRASH -- CONT WITH SCRATCH MEDIA ON DL003
    
    
    012642
    @?
    I also can enter small programs and they work fine. So what I'm looking for is a small memory program which can be loaded into PDP-11 memory and test all 2Mbyte and report errors. I have not tried XXDP (I'm not very familiar with thats why), but I could also try to boot XXDP with a memory test from a RL02 image, but I have no clue how to do that, so any advice how to use XXDP to test memory would be useful as well.

    Peter

  2. #2
    Join Date
    Jun 2012
    Location
    UK - Worcester
    Posts
    2,528

    Default

    The 'old' papertape maindecs for the 11 should work OK.

    I would look at how bytes are accessed on your memory card. This, invariably, could turn out to be the culprit...

    Dave

  3. #3
    Join Date
    Apr 2017
    Location
    Switzerland
    Posts
    224

    Default

    Found at least some of the reasons. At least I can now boot RT-11 and RSX-11M with my homebrew memory card. There was a problem with the fine tuning of the timing. So I can say that in general the memory card works, however I need to dig further into the timing setup to make sure it is 100% compliant to the Q-Bus.

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