Can't get crossfire working

[bobman0330]

Background:
I built this system about 4 months ago:
processor: E8400 @ 3.6GHz
mobo: Tpower I45
video card: Diamond HD4850, reference design
Vista 64

It worked mostly perfectly, except I would occasionally get crashes (sometimes with RSoD) during long, intensive gaming sessions. This happened maybe two times over 4 months when I was running my video card at stock speeds, but my system was never crysis-stable when the video card was overclocked more than a very small amount.

Problem:
I just got a new 4850 (Powercolor, modified cooling system; both cards are 512 MB). I installed the new card. My old PSU was ~450W, so I upgraded to a BFG 650. Tpower uses jumpers to activate the second PCI-E slot, which I switched per the manual (8x/8x). I uninstalled drivers (+ used driver sweeper in safe mode), then reinstalled.

In CCC, there should be a tab labeled CrossfireX to enable CF, but it's not there. Additionally, in the graphics hardware window, it shows the second card as "disabled adapter":

Primary Adapter
Graphics Card Manufacturer Built by ATI
Graphics Chipset ATI Radeon HD 4800 Series
Device ID 9442
Vendor 1002
Subsystem ID 0502
Subsystem Vendor ID 1002
Graphics Bus Capability PCI Express 2.0
Maximum Bus Setting PCI Express 2.0 x8
BIOS Version 011.003.000.000
BIOS Part Number 113-B50102-103
BIOS Date 2008/05/23
Memory Size 512 MB
Memory Type GDDR3
Core Clock in MHz 625 MHz
Memory Clock in MHz 993 MHz
Total Memory Bandwidth in GByte/s 59 GByte/s

Disabled Adapter
Graphics Card Manufacturer Powered by ATI
Graphics Chipset ATI Radeon HD 4800 Series
Device ID 9442
Vendor 1002
Subsystem ID 2266
Subsystem Vendor ID 1787
Graphics Bus Capability PCI Express 2.0
Maximum Bus Setting PCI Express 2.0 x8
BIOS Version 011.010.000.002
BIOS Part Number 113-BA0102-X07
BIOS Date 2008/09/09
Memory Size 512 MB
Memory Type GDDR3
Core Clock in MHz 635 MHz
Memory Clock in MHz 993 MHz
Total Memory Bandwidth in GByte/s 59 GByte/s

Device manager and GPU-Z both recognize the second card. GPU-Z has both running at PCI-E 2.0 x8 with CF disabled.

With my mobo set in 8x/8x with one card or two installed, I'm also experiencing freeze-ups (screen frozen, keyboard and mouse nonresponsive). These seem to happen randomly when I'm not doing anything graphically intensive (mean time to freeze is about 20 minutes, I'd guess). Launching a game leads to an immediate freeze though. Furmark stability testing , oddly enough, does not cause an immediate crash.

What I've tried so far:
Tested each card individually - both work solo
Switched which card is in primary and secondary PCI-E
Used catalyst 8.10 drivers from ATI, 8.9, and an older set that came with the Powercolor card
Installed both cards, then installed drivers
Installed one card, fresh driver install, then installed second card and reran driver install
Installed both cards, installed drivers, then used Device Manager to reinstall secondary card
Put my crossfire bridge in every conceivable orientation (I only have one at the moment).

Questions:
ATI has been thoroughly unhelpful. Is there anything else to try before returning the new card and giving up?

Bonus secondary question: I suspect the RSoD crashes I had earlier are related to an underpowered PSU, so I'm probably not going back to the old one. Is that plausible?

Many many thanks for your help.

 

[bobman0330]

bump?

 

[Sam25]

Some people have had this problem with 2 X 4850's, you might want to give this a read:

http://forums.amd.com/game/mes...tid=262&threadid=99936