Re: Information about this SRAM card

[dempson@actrix.gen.nz (David Empson)]

Bryan Villados <news002@macgeek.org> wrote:

> I've never seen this card before....
> 
> http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=2070773121
> 
> Could someone post a write-up about this card? Thanks! :)

I've never seen one of these cards before.  The only visible components
are two 8 KB static RAM chips and a PAL (logic chip).  It is obviously
made by Apple, given the logo and corporate font.

Given that it contains 16 KB of RAM, I expect it is supposed to be
compatible with a language card.

The only useful reason I can think of for it containing static RAM as
opposed to dynamic RAM is that the contents of the RAM would be
preserved if the computer stopped refreshing memory for some reason, but
the only time it does that is when it is switched off, and the static
RAM contents would be lost along with everything else.  If it had a
battery backup option, it would make more sense.

It would also consume less power than a card with the same amount of
dynamic RAM, but that is pretty minor in comparison to the rest of the
computer.

According to the seller, it came from a IIe, which is possibly a
counterargument to it being a language card, as the IIe would have no
need for such a card.

It might be some kind of prototyping card, which has read/write access
to the $Cn00 and $C800-$CFFF space, with bank switching to provide
access to the rest of the RAM.

-- 
David Empson
dempson@actrix.gen.nz