Problem and question; AMP usage of ATI 5770?

[letigre]

Hello,

I recently upgraded my system and am experiencing an issue.

My current setup is
MSI P55-GD55 micro-ATX MOBO
Intel i5-750 CPU
Corsair 750w PSU
4G DDR3 Corsair Memory
ATI Radeon 5770 (XFX manu.) x2

The recent additions are
the Corsair PSU (750w up from a 550w)
And a second Radeon 5770

The issue I've been having is that I have noticed a loss of framerate in quite a few games when shadows quality is turned up after adding the second card. Before I even began toying around in games, I made sure they were both properly connected or working (through CCC), so I ruled that out as being the issue.

I've began thinking that it's my PSU, under-powering the cards. According to the manufacturer, the PSU puts out 60A on the +12v. My question to you guys is; Is this in fact the problem? I've done a bit of searching but can't find any concrete evidence. All I have to go on is that the game performance does increase when the second card is removed.

 

[millwright]

According to this test, you are not even close to overloading that power supply.

http://www.tomshardware.com/reviews/radeon-hd-5770,2446-15.html


That 324 watts is for the whole system. If it was all 12volt,(and it's not) that would only be 27 amps on the 12v rail, and that Corsair can put out every bit of 60 amps.


I'm not a big gamer, but I noticed that the benchmarks are close to the same, in some tests,1 card vs.2.

 

[Silvune]

Agree with millwright. To me it sounds a bit like a scaling/driver issue, maybe the games you're playing don't like crossfire?

Another possibility is that the slot that the second card is in, is very slow. According to the spec page of that mobo, the second slot is gen 1 and x4 speed, which I'd assume is very slow.

 

[banthracis]

A third question to ask is what version of Catalyst are you using?

Silvune probably got it right though. Xfire setups run at the speed of the slowest card, and using a x4 slot for the second card is also dragging down the performance of the first.

 

[letigre]

First off, thanks for the replies guys =].

I'm using CCC V. 10.5

A buddy of mine at the office suggested I check around for issues wit this particular game and crossfire. However I had no idea about the slower speed of the second PCI-E Gen on my Mobo and that seems to be the most logical answer here.

Just to be certain, I think I'll search around for possible xfire/driver issues before looking at new mobo's T.T

Thanks for the help guys =]