4850 CF issue?

[xt0m]

Hiya,

I've got some strange CF issues with two Club3D 4850's here. Each one runs flawless without the other attached but stick em together and nothing works. No matter what I do. Mobo is Asus Evolution with 0401 bios.

Here's what I've tried so far: (on both dirty XPSP3, clean XPSP2 and clean Vista SP1)

- put one 4850 in the top x16 slot: OK
- put the other 4850 in the top x16 slot: OK
- put one 4850 in the bottom x16 slot: OK
- put the other 4850 in the bottom x16 slot: OK
- put both 4850's in blue x16 Crossfire: either no post (out of sync lookalike) or boots and stops when loading windows
- put one 4850 in x16 and the other in x4: both cards are detected and installed, but no CF possible
- been using Catalyst 8.6 with and without hotfix
- tried giving each card its own 6-pin PCIe wiring
- tried with one and two CF connectors

Running out of ideas here..