IMSAI (moving along...)

From: Dave Dameron <ddameron_at_earthlink.net>
Date: Thu Jul 8 10:52:58 1999

At 02:41 PM 7/8/99 -0400, Bill wrote:
>> 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;
...
Yes, many static memory cards powered up with blocks, usually 2^x bytes of
data equal or approx. 0FFh or 00h.
I can understand how this would happen in byte wide rams like 6116 and
later where the bits in each byte could be physically related, but it also
happens in bit wide rams such as 2102's.
I would follow up on the posts about "Mwrite" signals.
Mwrite = S100 pin 68, active high,
pWR (processor write) = S100 pin 77, active low.
-Dave
Received on Thu Jul 08 1999 - 10:52:58 BST