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27813Re: [midatlanticretro] EconoRAM VIIA Issues

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  • Kyle Owen
    Oct 24, 2012
      Here's something I've noticed: if I have the board configured as 8k at $0000, 8k at $2000, 4k at $4000, and 4k at $5000, everything works fine. It doesn't matter which 4k or 8k bank is where; all configurations like the above work very well.

      When I configure it with either 4k bank at $0000, things begin to fail. Only the 4k bank at $0000 has problems, and again, that's either 4k bank. When either bank is positioned anywhere else, it works just fine. When either 8k bank is positioned at $0000, it works fine. But when any 4k bank is at $0000, writes (or maybe reads) become messed up. 

      And by messed up, I mean sometimes it'll write, and sometimes it won't. I believe the problem is solely based on writing, as the reading back shows some $A6s and some $6As after my RAM test, where good RAM will show all $6As. There are no signs of bent pins, and all chips have been reseated. And again, in the 8k-8k-4k-4k configuration starting at $0000, everything is working fine. Only in a 4k-4k-8k-8k or similar approach, with any 4k bank at $0000, do things begin to not work. 

      I'll take some screenshots of the RAM tests when I get back from work. 


      On Wed, Oct 24, 2012 at 6:52 AM, Bill Sudbrink <wh.sudbrink@...> wrote:

      Are you seeing "garbage" when you get an error or $A6
      when you expect $6A (or vice-versa)? This might clue
      us in to the "level" of the problem. Garbage would
      indicate a complete read or write failure, while the
      reversal error would be more likely to indicate an
      address decode error. I would look very carefully for
      bent pins. I have seen board where the pin was
      crumpled directly beneath the chip, sometimes making
      electrical contact with the socket, sometimes not. I
      don't have time to look at the schematic now, I'll see
      if I can make time at lunch.

      Bill S.

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