This is going to be a club swung.

[NJ5]

I've done a little research:

- 360's OS takes up 32 MB of memory (6.25% of the memory). That leaves 480 MB for developers to split as they like between graphical and regular RAM. Meaning that if you split it equally, you have 240 MB for each use.

- PS3's OS (in the latest firmware update) takes up 48 MB of main memory (18.75%) and 24 MB of graphical memory (9.375%). That leaves 208 MB of RAM and 232 MB of graphical memory for developers.

Sources:

http://www.innerbits.com/blog/2007/08/21/ps3-180-sdk/

http://www.innerbits.com/blog/2007/05/09/ps3-memory-footprint/