68k user RAM

Sometimes called "work RAM".

64KiB mapped in the 68k's memory space, from $100000 to $10FFFF (mirrored up to $1FFFFF on cartridge systems.

The range from $10F300 to $10FFFF is used by the BIOS functions and shouldn't be used as regular work RAM.

In CD systems, the 68k's RAM is used in the same way, but is located in part of the program DRAM instead of in separate static RAM chips (?).

Is it always cleared out by the BIOS ?

Z80 user RAM

2KiB mapped in the Z80's memory space, from $F800 to $FFFF. Not automatically cleared.