ATI 5970 Radeon HD question

Now, most of us know that the card is a single card with multiple GPUs. And from what i've understood after looking into the card info and specs, i realized that each GPU has it's own memory, 1 gb for each. Windows and other GPU software recognizes the device and treats it as 2 cards instead of one, as in an ATI crossfire mode. Some applications support that mode and some do not. (i.e. games)

I got 2 questions now:

1- In Crossfire mode, and when running a game for example, it will only detect 1gb. What's the use of the other 1gb that is reserved for the other GPU?

2- How can I be certain that the 2 GPUs are working together, because i use CCC ATI and it shows that the GPU is not doing anything?


Note: I tried the "test custom clocks...." button and made sure that the gpu is working.