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Thread: 5150 Not Passs Mem Refresh Test

  1. #11

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    Quote Originally Posted by KLund1 View Post
    There is still know way to ID which individual chip(s) are causing the problem.
    I just have to find some time to alter my diagnostic ROM as proposed above. The difference in the written and read value should point to the offensive bits.

    Also the ground and + volt pins are really hard to get out without some damage to the hole and/or the board.
    I recognize the problem. In the worst case AND having enough spares of the IC, I just cut it out the board (cutting it at the top of each pin). I then only have to worry about one pin each time.

    Is there are procedures to use a logic probe to find the bad chip(s), perhaps?
    Assume the 8253 timer signals the 8237 that it is time to refresh the DRAMs but the signal never arrives for what ever reason. I doubt very much if you can see the little blip wit a probe. A logic probe? No, or you have to be very lucky.
    A oscilloscope would do better. Much better would be a logic analyzer. But the prizes are "better" as well.
    Unless you have a lot of time at hand, wait for my new ROM that will tell you why the 2 KB RAM test failed.
    With kind regards / met vriendelijke groet, Ruud Baltissen

    www.baltissen.org

  2. #12

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    Big bummer: I found a bug in the memory test. I already found the test quite fast and I thought that were my programming skills. Checking to find a way to output the reason why the 2 KB test halted the diagnostics, I saw that I used register DX twice: once to save the contents of CX and once as I/O register. It meant that, instead of restoring CX with its original value, it was written with this I/O value, 61h, instead. 97 or something like 2048 is a big difference. And why did I use DX in the first place? 61h can be used directly as well in an IN or OUT command.

    To make things sure: this bug could never cause the error KLund1 ran into.
    With kind regards / met vriendelijke groet, Ruud Baltissen

    www.baltissen.org

  3. #13
    Join Date
    May 2006
    Location
    Melbourne, Australia
    Posts
    6,237

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    Quote Originally Posted by KLund1 View Post
    The system had the 1983 BIOS upgrade. There was a HD in the computer so they need that upgrade.
    Per [here], that will be a 1982 dated upgrade (10/27/82).

    Quote Originally Posted by mikey99 View Post
    What symptoms do you observe when the board boots with the original ROM chips.
    Quote Originally Posted by KLund1 View Post
    On normal boot I get 1 long beep.
    Ruud's soon-to-be-modified diagnostic may reveal a bad RAM chip (or chips) in bank 0, however I am curious about the long beep you are hearing from the 10/27/82 BIOS.

    The breakdown of the POST in the 10/27/82 BIOS is at [here]. The only single beep is at step 27, and that is a short beep, not a long one.

    And, if there is indeed bad RAM in bank 0 (16KB sized on the 16KB-64KB motherboard), the POST would halt the CPU at step 13, which is before any of the steps that issue any beeps.

    So, puzzling.
    How long, in seconds, is "long" ?

  4. #14
    Join Date
    Jun 2012
    Location
    Livermore, CA
    Posts
    285

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    Ruud,
    Thanks for the input. I am glad to be of help. Let me know when the new ROM code is ready and I will burn an eprom, and test on this board. For me, finding the issue with the 1st 16K has been difficult on many boards. Some I have yet to solve. Those boards are gathering dust, awaiting a fix so a new user can appropriate them.

    modem7. I as gong from memory on the beep. I will reconfigure to original chip set and report back with accurate data.

    As always, I very much appreciate all your help in my learning process with these vintage machines!!
    Atari Falcon030, Atari MSTE, Atari PS3000, STACY 4, 4160STE-CosmosEX, Atari PC1, 400/800/1200XL,800XL,800XE,130XE, XEGS, Apple IIGS, TRS-80 4P, TI 99/4A, Co-Co 3, Amiga 500, C64/128D

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