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2x 4850 - Strange Crossfire Issues when enabling/disabling

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Mechcommander

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Hey folks,

Not sure if anyone can help me out with this or not, but any advice is certainly appreciated.

Here's the story: So, I was able to get in on that Core i7 $180 deal at Microcenter a couple weeks back, and I decided to just go with a whole system upgrade. I switched to the i7, 8GB of DDR3, a 650w Antec Earthwatts PSU, and a new SSD from a Phenom II build. The only thing that stayed the same between the two systems was the graphics cards - a Visiontek 4850, and a Gigabyte Radeon 4350 which have worked great for me the past couple years.

So, Newegg recently has a good deal on another 4850, and another card fro crossfire is a cost-effective performance boost. I pick one up (Sapphire 4850) - the card comes in, I install it, and this is where the weirdness starts. I originally had the two card to drive three monitors, so I wanted to keep all three in the system to have Crossfire enabled and have the third card drive the third monitor. Turns out that hosed my system completely (I'm thinking it's a motherboard limitation since the 3rd PCI-E slot is only 4x capable), so I was forced to use the two 4850's.

I hooked up the 4850's with the Crossfire cable, restarted the machine, and reinstalled the latest drivers. Crossfire was enabled without issue, and my performance in Crysis was superb. Now, this required disabling my 3rd monitor to use Crossfire - I figured I could live with turning on Crossfire when needed and then flipping it off to get all three monitors going again.

So, after flipping on and off Crossfire a few times for a few games, I come out of Crysis, and turn off Crossfire. My displays flicker like usual, and then I get nothing displaying on the two displays running off my master card (they detect that an image is *supposed* to be going to them - they are not in sleep mode). Long story short and a lot of troubleshooting later (including a full new install of Windows 7), this behavior keeps occurring. No amount of driver uninstallation, different versions, or reboots fixes the issue. I have to swap the cards to each others' PCI-E slots for everything to work again.

I heard using Crossfire with different brand cards can cause problems, but this seems really weird. Any ideas, or am I looking at selling the old 4850 and just waiting to upgrade to a 5850 at some point?

Thanks in advance for the help!
 
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well they suppose to work different manufactures so that shouldn't be the problem. as for the 3rd card crippling the system to drive the 3rd display that shouldn't be an issue since it mainly 2d so 4x shouldn't be an issue. you should have enough power in the 650watt to drive all the cards and system as long as none are oc. that really weird don't have answer for you. 5850 will be pretty close to the 4850 in crossfire. so i guess that always an option. after you swap the card and do the setup for all 3 displays does it work then ? or does it crash down to ?
 
No, unfortunately - it seems having three video cards in the computer just hoses it - windows takes around 5 minutes to boot, and then I'm lmited to one output on the main 4850 at 800x600. No idea what the issue is when three cards are in. I'll try updating the bios on the p6t and see what happens but I'm notoptimistic at this point.

Thanks for the help though - it's good to hearthat the configuration should work at least.
 
after the computer locks up the crossfire displays and you exchange card in their slot. do you have to set back the whole system setup again ? if doesn't require re setting up when you between crossfire and normal modes does it lock up again ? easiest solution might be just to upgrade to the 5850 to run all three displays or TripleHead2Go to solve the problem if you don't want to upgrade rite now but it is limited to 3 x 1680 x 1050 or 2 x 1920 x 1200
 
No, I do not have to set the whole system up again after exchanging the cards. Windows re-installs the cards and the original problems repeat; I can use Crossfire fine until I need to turn it on and off a couple times.

I think you're right - sounds like a USB -> DVI solution or a 5850 would be best, but unfortunately the 4850 was the only money I had for an upgrade at this point.
 
humm for how you describe it working it sounds like a windows problems with the driver with how its reacting but you did a fresh install. so can't think of any other issue that would cause that. you could just run the card separate to keep all three monitor and just game on one 4850 if that is adequate. can't see any other short term solution
 
Sorry for the thread res, but I've actually purchased another exact model of the new 4850 I purchased, and Crossfire now works just fine. In case anyone else has this issue, here are before/after configurations:

Before: 1x Sapphire 4850 (Model #100245HDMI), 1x VisionTek 4850 (SKU #784090025043) - Caused issues switching between Crossfire on/off.

After: 2x Sapphire 4850 (Model #100245HDMI) - no issues switching between Crossfire.

Glad it wasn't another component or something. Nice that I didn't need to purchase a 5850 to fix it. :)
 
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