|Fast facts on the CD BackUp RAM Cart|
|Made for: Sega Mega-CD|
The CD BackUp RAM Cart (バックアップＲＡＭカートリッジ) is a memory card designed for the Sega Mega-CD that plugs into the Sega Mega Drive cartridge port. It is for use with Mega CD games which require the user to save, as unlike ROM cartridges, there is no way of saving data on the disc itself. The unit contains 2045 blocks (1 Mbit) of memory for game saves.
For the North American version, the cart resembles a regular Genesis cartridge, aside from a blue edging saying "Sega CD", as opposed to the usual red edging found on standard Genesis cartridges. Some RPGs - most notably Shining Force CD - used this for memory, as there was often not enough space for the save files in the internal backup RAM. In the case of Shining Force CD, this cartridge allows the player to unlock the last story segment of the game, inaccessible without the backup cart due to the Sega CD's internal memory limitations.
While the only officially-released RAM cartridge for the Sega CD has a capacity of 1 Mbit (128 KB; 2045 blocks), the system actually supports up to 4 Mbit (512 KB; 8189 blocks). The memory size is specified by a 3-bit value mapped to Main 68000 address $400001. This value indicates the memory size as a power of two, multiplied by the base memory size of 8 KB.
| 3-bit Value
|Size (Kbit)||Size (KB)|
|000||64 Kbit||8 KB|
|001||128 Kbit||16 KB|
|010||256 Kbit||32 KB|
|011||512 Kbit||64 KB|
|100||1024 Kbit||128 KB|
|101||2048 Kbit||256 KB|
|110||4096 Kbit||512 KB|
|Sega Mega-CD Hardware|
|Mega CD Variations||Wondermega | LaserActive | Sega Multi-Mega | CSD-G1M|
|Misc. Hardware||CD BackUp RAM Cart | Mega-CD Karaoke | Pro CDX|
|Development Tools||SNASM Mega-CD, PsyQ Mega-CD SDK|
|Cancelled Hardware||Game Genie|