Apparently, a 2.1 slot (which I've never actually seen. As far as I know the slots on most boards are 1.0, 2.0 and 3.0) is capable of 150W from the slot, but the PCIe standard usually calls for 75W from the slot, which is why most mid-range and above cards need an extra power connector.
A 6870 HAS such a connector (maybe two), so it wouldn't need to pull more than 75W from the slot anyway. That's probably the reason you didn't notice it (although I must admit, I didn't even know you COULD increase the wattage available from the slot. I wouldn't figure that it would be safe, especially 250W).
oohhh...i knew that, it gets the rest of the power from the 6 pin connectors. i'm a dummy. thanks!