Graphics Cards not 100% on Crossfire

[GustavoGimpel]

I just bought a cheap used XFX R9 280X Black Edition to crossfire with the one I already have of the same model. Setting it up was a nightmare, and after messing up with DDU and reinstalling AMD drivers, the Crossfire is finally working. While gaming, on some titles like The Witcher 3 and Doom 2016, both cards ramp up to 99% and I've got a huge bump in fps. But on some other titles, both cards stay around 50% both. Rocket League both cards stay at ~70% and the CPU sits confortably at 40-50% usage, on CS:GO same thing happens but CPU stays even lower, so I'm confident it is not a CPU bottleneck. I'm using the latest AMD drivers alongside Windows 10 with the Creators Update. I disabled ULPS and set the Graphics Profile to Optimize Performance on the Radeon Software. I disabled any kind of sync like V-Sync in all games.

On some games, the card usage is so low that it won't even boost to the maximum frequency. Is there any configuration I am missing out? Thanks.

My specs:
Asus Crosshair V Formula-Z
AMD FX-8350 @ 4.7Ghz ( Cooled with an H100i )
2x AMD R9 280X XFX Black Edition
NZXT Hale90 80+ 1000W Power Supply
8Gb DDR3 G.Skill Ares 1600Mhz
Samsung 840 Evo 120Gb
Seagate Barracuda 1Tb 7200Rpm

 

[pentium4inside]

some games dont make use of crossfire. in those, the usage would be low.

 

[Rexper]

And what sort of FPS are you receiving and what monitor are you using?

 

[GustavoGimpel]

I know that some games don't support Crossfire, but shouldn't those games just disable de second card e use only the first? I tought that on those scenarios the system would behave as if it had only one graphics card. And I also tought CS:GO and Rocket League had Crossfire/SLI support.

I'm using MSI Afterburner with Riva Tuner to check in game and HWMonitor + AMD's Crimson software on a second monitor.

On Rocket League, even tho both cards are running at 70/70%, i'm getting high FPS, around 180 on a 1080p ultrawide monitor. Before I was getting around 110. CS:GO on the other hand I'm getting less FPS I did when I only had a single card, interestingly, even tough still high FPS, around 120 now and around 200+ before. There are other games like Unreal Tournament 3 which I'm getting way lower fps than when I had a single card only, about 60 with v-sync off: the cards run at 30/10% only.

I'm not asking this question because I want 999999 fps, all games are playable, I just want to understand what's going on. I knew beforehand that some games wouldn't support CF and some wouldn't even start, but I've never heard of games performing worse in CF. Thanks for the replies.

 

[pentium4inside]

when crossfire is not supported, the performance is even worse than a single card performance

 

[Rexper]

Crossfire and SLI have many problems, which mainly depend on the game played. Sometimes only one card is supported, so one card isn't used at all. Sometimes both cards are used, but not to their best. Sometimes crossfire / SLI actually decreases performance, which has been proved on Hardware Unboxed.