HD7790 Crossfire strange core clock behavior

Flymanos

Honorable
Dec 21, 2013
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10,510
Hi,

First of all, i know that crossfire isn't the easiest thing to deal with, but I received the second card from my sister so i try to get it work :p

I've got two ASUS HD7790 1GB running on crossfire 8x/8x, on motherboard A970-G46. Both overclocked to 1200mhz on core. When I look on Afterburner Hardware Monitor, it shows that the clock constantly changes. http://prntscr.com/2csuci When I play, it never reaches 1200mhz, or even 1000mhz. Performance is also terrible, very often it's better to play without second card. Efect fades only when I remove second card, switching off crossfire doesn't help. Any idea what do i have to do? I installed 13.12 WHQL drivers, but it didn't help.

PSU: SilentiumPC Deus 600W | CPU: AMD Phenom II 965 @ 4.0GhZ
 
Solution
I tried using one for folding and saw that it couldn't maintain a flat line when under a constant load so I think it's either the architecture or drivers myself.

_Vass

Honorable
Nov 24, 2013
604
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11,160
the psu should not be the problem. it is not a super cheap psu. Both of the cards have to be at the same speed to run well. you problem might be; 1 card can't hold up> downclocks> pulls down the other card
 
G

Guest

Guest
I think your gpu's supports PCI-Express 3.0 but your mobo supports only 2.0?
It does matter with the performance of your gpu.
 


I'd say that was an unlikely reason, PCIe 2.0 has been around for a while so the majority of boards are going to be PCIe 2.0 and it makes little sense to have a card that is not backwards compatible and requires a new motherboard.