Crossfire Help

[sir-les-mp]

Ok im going to assume im being a little nieve here but will ask what im going to assume is a fairly silly question.

I recently purchased 2 MSI R9 280x video cards from the MM to run in a crossfire setup.
This so far has been working fine but i am wondering why both cards when playing games do not show the same amount of GPU Load.

My understanding of both crossfire and sli is that both cards are used to render the image on screen alternating between each other as to wich frame is being rendered ( i.e gpu1 renders framse 1,3,5 7 etc and gpu2 renders 2,4,6,8 etc )
Which to me would suggest when gaming or doing any other graphic intensive task they would show the same amount of GPU load each.

The upshot of having either Crossfire or SLi is improved graphics performance and an increase in FPS in games etc over a single video card ( i am aware the FPS increase is only about 15% or something in that region )

So now to my querry, if my understanding is fairly correct and both gpus should be showing the same GPU load when gaming then i must have missed something in one of the settings as whilst playing my MMO's of WoW and SW:TOR i noticed via GPU-z that the GPU load on both cards is not the same which leads me to the conclusion im getting very little if any benifet of having 2 video cards in my system

The system i run is as follows

i5 3570k @4Ghz
16 Gig DDR 3 1600Mhx Ram
2x 120Gig HyperX SSD in Raid 1
1x 1Tb Maxtor Mech drive
Water cooling on Cpu
and either a 750/850 Psu cant remember the brand or model no ( too lazy to open up the case to double check )

Windows 8.1 64 (due to go windows 10 in a few weeks)
Amd driver version 15.200.1046.0 WHQL (Catalyst 15.7)

 

[Meladath]

GPU usage isnt the same on both, in fact it almost never is. If its enabled in CCC then it will use the second card when it can. As long as your second card is setting 3D clock in games, then its using the second GPU. How much depends on how well the game is made, and how well the crossfire profile for it is. Crossfire only works with fullscreen games, NOT borderless fullscreen, other than a very select few anyway (I know, its ****, I have no idea why it doesn't support borderless fullscreen but it doesn't)

 

[andybird123]

I don't know about crossfire, but with SLI, if theres another bottleneck like CPU, when useage drops it drops on both cards e.g. Both cards run at 80%

If your having one card run at 99% and the other at something like 20% then it sounds like crossfire isn't working

 

[pandem0nium]

Are the cards running the same clockspeed and ram frequency?

If not, the lower clocked card will have a higher usage % to keep up.

The other reason I could think of is usually in a cf setup, the top card has higher temps. If the cards are using boost clocks, the top card may be throttling due to heat.

 

[sir-les-mp]

Both cards are the exact same spec and run 1020 core clock and 1500 memory clock.

as for temp the highest ive seen either card go is 75c with auto fan i have man set the fan at 60% when running games so this knocks the temps down to high 60's

One thing that was mentioned was the i need to run games in Full screen rather than windowed full screen which i tend to do so i can interact with my other programs on my second monitor ( which runs off the gpu on my i5 processor )

I did test this earlier and noticed a big boost in FPS as well as the 2nd card doing more of the work gpu load wise and a temp differrence of 6-7 degrees higher on the top or first card

But again the gpu load was quite differrent the 2nd card was around 80% and the first card hovering in the mid 40%

So gaming wise i need to revert to full screen rather than windowed full screen mode and set up my other programs and not interact with the as much whilst gaming it seems.

 

[Steveocee]

Yep, ensure full screen mode is enabled as otherwise I didn't even think crossfire worked. Try disabling ULPS as well as that can cause problems.

Try swapping the cards in the slots just to make sure it isn't a card problem at worst case.

 

[sir-les-mp]

Well it seems my issues i was having were down to a school boy error of not having my games in Fullscreen.

After a few hours raiding in WoW tonight in Full screen i did notice that the higher the FPS i get in darker areas of the map the more the 2 Gpu's seemed to match in GPu Load. The lower my FPS in brighter areas the bigger the differrence was between the two as far as GPU load was concerned.

Temp wise i also noted the the 1st GPu card did appear to at times have a temp 10-12 c higher than the second one which was doing the lions share of the work.
The max ive seen is 79c which i believe is a good 15c below where the gpu would start to throttle due to heat.