see Bank Switching
12K ROM
256 bytes RAM
Each bank must have the first 512 Bytes set to 0, it's to insure proper RAM read/write and also used as the mapper signature.
Address map
There's three 4K banks usable with this mapper by reading/writing to these addresses.
This will switch the chosen bank into the $F000 to $FFFF memory range.
| Address | 4K ROM Bank |
| $FFF8 | 0 |
| $FFF9 | 1 |
| $FFFA | 2 |
There's the 256 bytes of RAM, it's accessible in the first 512 bytes of the cart addresses
| Address | RAM Action |
| $F000 -> $F0FF | Write to RAM |
| $F100 -> $F1FF | Read from RAM |
Addendum
Alternate name: CBS RAM Plus cartridge.