At my wit's end with Crossfire, R9 280x's

[NocNautilus]

Just picked up a second R9 280x yesterday and have spent probably a total of 6 hours trying to troubleshoot this. Here's my build:

PCPartPicker part list / Price breakdown by merchant

CPU: Intel Core i5-4690K 3.5GHz Quad-Core Processor ($229.99 @ SuperBiiz)
CPU Cooler: Cooler Master Hyper 212 EVO 82.9 CFM Sleeve Bearing CPU Cooler ($26.99 @ Newegg)
Motherboard: ASRock Fatal1ty Z97 Killer ATX LGA1150 Motherboard ($89.99 @ Newegg)
Memory: Corsair Vengeance 8GB (2 x 4GB) DDR3-1600 Memory ($76.99 @ Newegg)
Storage: Samsung 840 EVO 120GB 2.5" Solid State Drive ($89.99 @ B&H)
Storage: Western Digital Caviar Green 3TB 3.5" 5400RPM Internal Hard Drive ($92.99 @ Amazon)
Storage: Seagate Barracuda 250GB 3.5" 7200RPM Internal Hard Drive ($27.00 @ Amazon)
Video Card: Gigabyte Radeon R9 280X 3GB WINDFORCE Video Card
Case: Fractal Design Define R4 w/Window (Titanium Grey) ATX Mid Tower Case ($105.99 @ Directron)
Power Supply: EVGA 750W 80+ Gold Certified Fully-Modular ATX Power Supply ($104.99 @ NCIX US)
Case Fan: Cooler Master R4-S2S-124K-GP 44.7 CFM 120mm Fans ($14.89 @ OutletPC)
Monitor: QNIX Perfect Pixel QX2710 Matte 60Hz 27.0" Monitor
Keyboard: Cooler Master Storm QuickFire Rapid Wired Gaming Keyboard ($73.99 @ SuperBiiz)
Mouse: Razer DeathAdder 2013 Wired Optical Mouse ($49.99 @ Amazon)
Headphones: Creative Labs Creative Fatal1ty Headset ($24.95 @ Amazon)
Total: $1008.74
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2015-05-16 11:26 EDT-0400

My single card Fire Strike score was 7437.
When using just the new card (in my second slot which I think has lower bandwidth) I get a Fire Strike score of 7109.
But WHEN CROSSIFIRING, my score is 6664. WHAT?

Performance is absolutely worse in games, lower FPS and they are acting far more unstable (tried BF4, Heroes of the Storm, and Witcher 2).

I've tried EVERYTHING I can think of: messing with CCC settings I saw recommended, both forcing Crossfire on all and just on apps that have profiles, I've reinstalled my drivers, I've flashed my motherboard to the latest firmware - nothing has helped. I'm at a complete loss at what to do now.

 

[WildCard999]

What are your GPU temps while gaming/benchmarks?

 

[sizzling]

Are there any updated BIOS's for your motherboard?

 

[madmatt30]

Are you using both crossfire cables ??

 

[sizzling]

What's your gpu and cpu usage during the benchmark? I did a quick search and the recommended minimum PSU seems to be 850w, normally not enough power results in random crashes but if its only just too much power draw for your 750w PSU maybe its causing performance issues

 

[NocNautilus]

Are you using both crossfire cables ??

No... wait, you are supposed to use two crossfire cables at once? I only have one, I only own one in fact. But I thought the fact that there are two crossfire ports was for when you use triple cards.

 

[NocNautilus]

What are your GPU temps while gaming/benchmarks?

The first card (top in my case) was around 80c most of the test, but at the very very end of the intense graphics part it got as high as 95c. Second card never went about 79c. I've got two fans pulling air in front of case, one pushing air out top, one pushing air out back. CPU's max was 80c during benchmark.

 

[NocNautilus]

Are there any updated BIOS's for your motherboard?

BIOS is updated to the latest, did it this morning as troubleshooting.

 

[WildCard999]

What are your GPU temps while gaming/benchmarks?

The first card (top in my case) was around 80c most of the test, but at the very very end of the intense graphics part it got as high as 95c. Second card never went about 79c. I've got two fans pulling air in front of case, one pushing air out top, one pushing air out back. CPU's max was 80c during benchmark.

GPU temp is safe. 95C is high but within safe operating temp. The CPU temp though is kind of high, does it get that high when you run a single GPU when testing?

 

[madmatt30]

You are only supposed to need 1 x crossfire cable but I had massive stability issues until I connected both together .

Its worth a go - you should have got 1 cable with each card ???

 

[NocNautilus]

What are your GPU temps while gaming/benchmarks?

The first card (top in my case) was around 80c most of the test, but at the very very end of the intense graphics part it got as high as 95c. Second card never went about 79c. I've got two fans pulling air in front of case, one pushing air out top, one pushing air out back. CPU's max was 80c during benchmark.

GPU temp is safe. 95C is high but within safe operating temp. The CPU temp though is kind of high, does it get that high when you run a single GPU when testing?

I know CPU is a bit high, I've actually got stock cooler on it with a shitty thermal paste. Arctic Silver 5 and the Hyper 212 EVO is in the mail, should get it by Monday and I figure that would clear that issue up.

 

[WildCard999]

I figured it might be thermal throttling and causing lower scores, one way of testing this is running a single GPU through the benchmark and checking the CPU temp. If its much lower then when it was tested with the CF setup then theres your issue.