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4MCS "Fix" for proper blinkin lights

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  • Grant Stockly
    Problem: MITS 4k static memory board is NOT Blinking lights compatible. Running program 00 00 00 00 C2 00 00 does NOT produce a faint 11000011 pattern on the
    Message 1 of 2 , May 17, 2007
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      Problem: MITS 4k static memory board is NOT Blinking lights
      compatible. Running program 00 00 00 00 C2 00 00 does NOT produce a faint
      11000011 pattern on the LEDs like it should! 8K seals card and 1MCS both
      correctly blink.

      Cause: The address decoding circuit, SMEMR, and PDBIN all combine to
      enable the data out buffers.

      Reason: The PDBIN signal is narrow and doesn't allow the bus to be driven
      very long.

      Solution: By removing the requirement for SMEMR to enable the data buffers
      the card looks like any other. Both the 1MCS and 8k SEALS card work this way.

      To Fix: Lift IC-F pin 10 and solder jumper from pin 10 to 12 on the same IC.

      Memory board now has dim 11000011. : D

      Grant
    • Grant Stockly
      ... A note for those interested... The jumper is placed ON the IC between pin 10 and 12. Not on the pads for the socket. Grant
      Message 2 of 2 , May 21, 2007
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        At 08:18 PM 5/17/2007, you wrote:

        >Problem: MITS 4k static memory board is NOT Blinking lights
        >compatible. Running program 00 00 00 00 C2 00 00 does NOT produce a faint
        >11000011 pattern on the LEDs like it should! 8K seals card and 1MCS both
        >correctly blink.
        >
        >Cause: The address decoding circuit, SMEMR, and PDBIN all combine to
        >enable the data out buffers.
        >
        >Reason: The PDBIN signal is narrow and doesn't allow the bus to be driven
        >very long.
        >
        >Solution: By removing the requirement for SMEMR to enable the data buffers
        >the card looks like any other. Both the 1MCS and 8k SEALS card work this way.
        >
        >To Fix: Lift IC-F pin 10 and solder jumper from pin 10 to 12 on the same IC.
        >
        >Memory board now has dim 11000011. : D

        A note for those interested... The jumper is placed ON the IC between pin
        10 and 12. Not on the pads for the socket.

        Grant
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