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Xfire mixed GPUs

post #1 of 3
Thread Starter 
Since i was recently sold a bum 4870, I now only have 1 4870, and two 4850s.

I started off with running the 4870 and the 4850 in xfire. Was stable at:

4870=790/1000
4850=700/1000
PHII= 3.5 by 200/17.5 @1.46v HT/NB 2600

3dmark06 scores were only 100points better than with two 4850s.

Then i added the third card, the second 4850.

GPUs stayed the same, how ever my now 3.5 OC was no longer stable, even with a few tried at upping the voltage.

I dropped it down to 3.4 by 200x17. My scores were now 300points higher than with the 4870/4850 combo.

Now obivously with the 100mhz loss on my CPU my score would be a little skewed, how ever, a 400point gain from a 4870 seems a tad low.

My questions are:

Am i running into a bottle kneck? Is this thanks to 64bit? Is heat a factor (i had to run my 4850s on air with the stock coolers and fans @60%)? Is tri-crossfire even worth it and will i see gains in games like crysis?
    
CPUMotherboardGraphicsRAM
Phenom II X4 940 Black Edition Asus M3A79-T Deluxe 2x HD 4870 CrossFireX Mushkin Red Line 4GB (2x2gb) 
Hard DriveOSMonitorKeyboard
Western Digital 500GB Green Edition SATA x2 RAID 0 Windows Vista Ultimate x64 Westinghouse 21.5" 1920x1080 Logitech G15 
PowerCase
Corsair TX750 Cooler Master HAF 932 
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CPUMotherboardGraphicsRAM
Phenom II X4 940 Black Edition Asus M3A79-T Deluxe 2x HD 4870 CrossFireX Mushkin Red Line 4GB (2x2gb) 
Hard DriveOSMonitorKeyboard
Western Digital 500GB Green Edition SATA x2 RAID 0 Windows Vista Ultimate x64 Westinghouse 21.5" 1920x1080 Logitech G15 
PowerCase
Corsair TX750 Cooler Master HAF 932 
  hide details  
Reply
post #2 of 3
That can't be a bottleneck. 64-bit shouldn't be a problem. Heat should not affect performance. I have never done Tri or mixed xfire before. I am also not familiar with 3D Mark to know if the increase in points is right.
post #3 of 3
when running to different cards be it a 4870 and 4850 or just different speeds on 2 4870s the faster card will always drop to the speed of the slower card so the 4870 is running at 4850 speeds so you wont get much more than crossfired 4850s
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