Sega CD/Saturn... memory?

Both the Saturn and the Sega CD had some internal memory to save your game. They both had a memory managers built into the firmware. Boot either system without a game and you can access it. It was also possible to get expansion memory cart's for both systems.

Also, the internal memory was run by battery, so if the battery died, so did all your saves on the memory. One reason why external memory carts were a great plus

The Saturn uses a battery to maintain the internal clock and the save files. The system will hang onto your files so long as the battery has power. Once the battery is dead, the internal memory is wiped clean. The battery can easily be replaced, but having one back-up cart to transfer your data to is a very smart idea.

The Sega CD uses a rather volatile Flash ROM for memory saving. If you don't power up the system at least once a month, you run the risk of having the memory dump your files. Also, it would seem that not playing it for extended periods of time can actually cause the internal memory to become corrupt. Once that happens, the console will never be able to save anything directly again. You will need a back-up cart.

Saturn internal memory: 447 k
Sega CD internal memory: 128 k