The 1kg wonder
Radeon HD 3870 X2 1024MiB in its naked glory. Two RV670 GPUs, a connecting PCIe 1.1 bridge, and two sets of 512MiB GDDR3 memory.
A single CrossFire connector lets you hook another X2 card for CrossFireX, promising rendering via four GPUs. The driver is still being worked upon, with effective four-GPU scaling proving to be difficult to attain.
As we alluded to earlier, the significant cooling is quiet enough for the single fan to spin relatively slowly.
Here is where much of the card's weight comes from, clearly.