I read a post here stating the Charge had 384mb of RAM free for apps, which 128 allocated to the CPU. Don't know if that's the case or not. However, I examined the Droid X2 and found that it did in fact allocate RAM for the CPU.
If I had to guess, I'd say that the amount of RAM allocated to the CPU changes depending on how much work it's doing. Don't quote me on that though!