Is the 3870 limited by 4x bandwitch.

I'd imagine it's limited somewhat, but with the crossfire bridge it shouldn't be too severe of a performance hit. I've only seen a few articles test 3870s in Crossfire, and none that tried to limit the bandwidth to only 4x. Here's an article that shows the performance hit with some other cards in single card configurations, so I'd assume the hit would be even smaller with Crossfire enabled.

http://www.tomshardware.com/2007/03/27/pci_express_scal...

I would not bother with CF in a 4x Slot.
There seems to be significant throttling on the 8800GTS with the 4x slot on some games.

The 3870 would likely see similar results.

No its fine, all tests using 8x8 and 16x4 showed like 1% difference, itll be fine.


One card in a single 4x slt however is a different story.