This is the first time i use CF.

Spec: 
Core i5-3570k @ 3.4 
DUAL Ati 7950 3GB
750W PSU 
16 GB Gskill Ram 

I just got another ati 7950 to (total of 2 right now). I put in the new card, put on both Crossfire Bridge ( each card has 2 CF, i got 1 CF connector from each card, so i figure i will just both of them on). Go to CCC and enable Crossfire. When i run game like Tera, i see that only the main GPU has the usage at 50%, and 2nd GPU does not run at all. Then i run Furmark GPU Stress Test, it shows that only the main GPU has the usage at 99%, while the 2nd GPU's usage only at 0%-5%. Why it that? Then i play Crysis 3 Beta, Yesterday i plays C3 with only 1 card at highgest setting and get aroun 23-35 FPS, today with CF i get around 30-40, this time while playing C3, the second card did run, but i thought the CF performance should be close to double the performance of 1 card. Can someone explain for me pls ? :)

Make sure you've got both the latest video drivers and also the corresponding version of Catalyst Application Profiles.

There's also the question of whether there are any gains to be had from adding GPU power.  If you were already limited by the CPU or an arbitrary limitation on frame rates with one card, then the most sensible thing to do when you add a second card is to ignore it and just use one.

CrossFire, like SLI, is very hit and miss.  Sometimes it works and sometimes it doesn't, even when there are gains to be had.  AMD and Nvidia do tweak some things on a per-game basis to try to make multi-GPU scaling work better, but they only hit the big name games.  If you're playing a beta, then the tweaking hasn't necessarily been done yet.

Also, if Crysis 3 is much like Crysis 1 or 2, then it's more benchmark than game, and getting low frame rates on powerful hardware is a feature of the game, not a bug.

While we're here, what power supply is that?  Two Radeon HD 7950s will eat a ton of power, so while a high quality 750 W power supply would be able to handle the load, a cheap junk one probably won't.

This is the one i am using: 

http://www.newegg.com/Product/Product.aspx?Item=N82E16817371025

Originally posted by dg29031994

This is the one i am using: 

http://www.newegg.com/Product/Product.aspx?Item=N82E16817371025

That power supply should be fine.  Do make sure you've got the latest drivers, though.

Do you get frame rate problems in TERA?  If not, then what's the problem?  Try disabling CrossFire and checking your GPU usage with just a single card.  If it's 50% that way, too, then you're bottlenecked somewhere else--which isn't necessarily a bad thing if your frame rates are high enough.

I should be more clear :D I am not playing at 1080p, i am playing at 1440p. 27: monitor from asus.

Here  is what i got after testting:

Tera at 1440p

---Single 7950:

      55-70 fps (hightest setting)

      GPU usage: 99%

---Crossfire 7950:

      55-70 fps (hightest setting)

       GPU usage: 99%

                               0% (second gpu)

If i play tera at 1080p i can easily hit 80 fps, i don't know if it can go any higher than 80 because it stucks 80 and won't go any further.

Crysis 3 at 1080p

---Single 7950:

     35-45 fps (highest setting)

     GPU usage: 99%

---Crossfire 7950:

     35-45 fps (highest setting)

     GPU usage: 99%

                            0-30% (second gpu)

Crysis 3 at 1440p

---Single 7950:

     25-35 fps (highest setting)

     GPU usage: 99%

---Crossfire 7950:

     25-35 fps (highest setting)

     GPU usage: 99%

                            0-30% (second gpu)

Well you can see, they are identical :P

Correct me if i am wrong. SHouldn't they be sharing performance ? I notice that the second GPU will run only when the first gpu hit 99%, i thought they would split the work half and half.

Originally posted by stayontarget
I have seen people post screenshots of tera using crossfire so i know it can work (SLI is not supported though).  To be honest I'm not sure how you set up crossfire, but I wish you luck.

How should i setup my CF? :P i honestly don't know. I pluged both cards on the mobo, put on the bridge, go to ccc and enable CF. Am i missing anything ?

If you're at 99% GPU usage, then it's extremely probable that the video card is the limiting factor.  And yeah, that sure looks like CrossFire isn't kicking in at all.

Make sure you have both the latest drivers and also the latest CAP:

http://support.amd.com/us/gpudownload/windows/Pages/radeonaiw_vista64.aspx#1

CAP didn't matter before with just a single card, but now that you're using CrossFire, you need it.

Furry doughnut time.

http://www.techspot.com/downloads/5462-furmark.html

Originally posted by Grunty

Furry doughnut time.

http://www.techspot.com/downloads/5462-furmark.html

I did that earlier, only one GPU run, the other one does not.

May require a BIOS update - I've had that happen to me once with SLI. Updated BIOS - it worked fine. It could also be that your second card doesn't work... I'd try playing with only the second card installed.

Here is the Heaven Benchmark Test. Big Difference b/w Single and CF.

Single:

Crossfire:

Base on those pic i assume that the crossfire does work.

After i do the benchmark, i test Crysis 3 again.

---Single card: while in this mode, i have around 25-32 fps In Game. But before i enter the game, at the Menu screen, i have 170 fps.

---Crossfire: While in this mode i have same In Game fps while in single card mode. But in the Menu screen, i have 220 fps.

So i guess i have low ingame fps because the game is still in beta ?

After Crysis 3 i test Tera, and i have same FPS in both mode.

Originally posted by miguksaram
Not so sure about Xfire as I haven't used it in awhile but at least in the case of SLI with the Furry Donut you can tell if it's enabled by the vertical line that will appear while the test is running.  I'd check to see if xfire has a similar effect and then be sure you seeing said effect.

Yeah, i used Furmark to test. I notice one thing, if i'm in fullscreen mode, both GPU will run, one will be 99% usage, other will be around 69% usage. If i am in Window mode, only one GPU runs.

If I'm not mistaken, CFX has never worked in windowed mode, and SLI only does sometimes (with the proper driver optimizations)

Originally posted by dg29031994
So base on my informations that i gave, does it look like i have any problem running CF? The benchmark looks good, the game looks completely opposite.

One search in google appears to provide your answer regarding TERA...http://tera-forums.enmasse.com/forums/general-discussion/topics/TERA-doesnt-support-Crossfire

Also you may want to ensure you running the game in Full Screen mode and NOT Full Screen WINDOWED mode.  As previously stated crossfire is not windowed mode friendly.

https://forum.tera-europe.com/showthread.php?t=124627

Originally posted by dg29031994
Ok, after testing Crossfire on BF3, the Crossfire worked fine. I have 100+ fps at 1080p ultra setting and around 100 fps at 1440p on ultra setting. I guess it does not work for Tera because like miguksaram said, Tera does not support crossfire, And it does not work for C3 maybe because the game is still in Beta and does not support crossfire. Thanks All

Most beta's don't support SLI/Xfire because it's such a small portion of the overall populace who will play their game to begin with.  So that really isn't surprising to hear at all.