The DRAM Cartridge is an add-on device adds additional DRAM to the Saturn for caching content from games. They came in two different sizes: 8 Mbit and 32 Mbit.
It's mapped on the A-bus CS1 area. For the sake of simplicity, here's a list of the addresses used by developers.
|0x22400000-0x225FFFFF||On a 8 Mbit cartridge, 4 Mbit is allocated here and is mirrored every 0x80000 bytes. On a 32 Mbit cartridge 16 Mbit is allocated here instead.|
|0x22600000-0x227FFFFF||On a 8 Mbit cartridge, 4 Mbit is allocated here and is mirrored every 0x80000 bytes. On a 32 Mbit cartridge 16 Mbit is allocated here instead.|
|0x24FFFFFF||Cartridge ID. This will be 0x5A for 8 Mbit cartridges or 0x5C for 32 Mbit cartridges.|
After initializing everything, you use it like a regular modem. To receive interrupts from the modem, enable SCU external interrupt 12(vector 0x5C).
Games known to support the DRAM Cartridges
- Final Fight Revenge