Carts for the 800XL/130XE

[cbmeeks]

Looks like the store is still down. :-(

 

I found the temp store and was looking at the carts to make 16k games for the A8. Why only 16k? Where there any 32k-64k game carts?

 

Looking at the pinouts, it looks like there are only 12 address lines (4k). But I see a "~S4 Chip Select--$8000 to $9FFF" and a "~S5 Chip Select--$A000 to $BFFF".

 

So does that really mean you are limited to 16k and you have to bank switch from the two 4k banks?

 

Also, any advice on how a budding amateur electrical engineer could learn how to create my own carts for the Atari?

 

Thanks for any suggestions.

 

cbmeeks

[Rybags]

There's numerous bank switching schemes in use. The Help system in the Atari800Win+ emulator describes them pretty well.

 

Of course, employing bank-switching means either extra hardware or having EP/ROMs with the extra logic built in.

 

The most basic cart is usually 8K ($A000-BFFF), then you have 16K ($8000-BFFF).

 

The OSS carts like Action and Mac-65 employed a system where $B000-BFFF was always present and $A000-BFFF was switchable among 3 4K banks, or could be turned off entirely to allow access to RAM at that address.

 

These days, you have things like the AtariMax flashcart which has banking to allow 128K or 1 meg total cart space.

 

But, regardless of whatever system is employed, a cart can only have memory residing in the 8000-BFFF or A000-BFFF area. Unsure if B000-BFFF is valid.

 

There's also the CARTCTL line which allows $D500-D5FF access, which is usually tied to a logic IC which performs the bank switching.

Some people have made devices which allow a page of RAM to instead appear there.

 

It would in theory also be perfectly valid to have a ROM to be pagable to that address area, although the usability is quesionable, and other means then need to be employed for bank selection.