Re: 128 K RAM Card for ][ Plus

[toddpw@lust.ugcs.caltech.edu (Todd P. Whitesel)]

gareth@freenet.vancouver.bc.ca (Gareth Jones) writes:

>Can anyone tell me about a Slot 0 memory card for the Apple ][Plus that 
>has 128K of RAM? It doesn't have a cable that connects to the 
>motherboard, the way some slot 0 cards did. It is a full-size card. There 
>are 4 red LEDs on the top (for banks of RAM?). There's no manufacturer's 
>name on it. The largest chip on it is by Motorola, and it has the 
>following identification "MC3242AP" then "QQ8327" on a separate line.

That big chip is a DRAM controller which handles the refresh and address
decoding (which is what most language cards used the cable for).

>I'd like to emphasize that it's working fine as a 16K language card, but 
>I'd like to find out how to access the rest of the RAM for a ProDOS 
>RAMdisk. Any ideas?

Two companies pioneered these types of cards. The two standards that resulted
are now referred to as "Saturn" and "Titan" which I think came from the
product names for each card (or maybe the company names, I forget).

I have a Saturn compatible card which also has that chip on it. This card
was programmed by using $C084-C087 and $C08C-C08F to bank switch the eight
banks of 16K that were available for the card. I wrote a P8 ramdisk driver
for it once; you either have to stake out some main memory somewhere (good
luck) or you have to put the copying code in the same place on all eight
banks of the card. $FFxx is the best page to use, because you have to make
sure the interrupt/reset vectors are reasonable or else you have to disable
interrupts whenever other banks are switched in.

Todd Whitesel
toddpw @ ugcs.caltech.edu