IMSAI (moving along...)

From: Bill Sudbrink <bill_at_chipware.com>
Date: Thu Jul 8 13:41:24 1999

> Many 8K static memory boards had provision for battery backup.
> Some cards used S100 pin 14 for this. These diodes were to feed
> the battery voltage to the VR outputs. They are not required if
> you are not using a backup battery with this card.

Yup! That's just how they are wired. Now, I've just put it back
in, and the behavior has changed! I still can't DEPOSIT anything,
however there does now seem to be data in the card. It's in an
interesting pattern (excuse the C syntax):

  if (address == 0x0000)
    data = 0xCF;
  else if (address & 0x0200)
  {
    if (address & 0x0002)
      data = 0x00;
    else
      data = 0xFF;
  }
  else
  {
    if (address & 0x0002)
      data = 0xFF;
    else
      data = 0x00;
  }

Do static RAMs just power up with random data or does this indicate
some kind of crossover between the address and data lines?

Thanks,
Bill
Received on Thu Jul 08 1999 - 13:41:24 BST