6870's CFX worse performance than single Card

Matthew Share · Oct 7, 2013

Hi guys

Problem:

My crossfired 6870's yields a worse performance than a single card. On all of the games I've played, I got the same problem. (League Of Legends, NBA 2k14, Crysis 2, DMC5, Grid 2, etc) For example In LoL, I would get a stable, non-stuttering 180 frames with CF disabled, but with CF I only get 80 and with a lot of stuttering. I turned it to the lowest setting, and I'm still getting the same low fps with CF disabled. With other games like NBA 2k14, I would get about the same FPS with CF both disabled and enabled, but it stutters a lot with CF enabled. I ran Crysis 2 on ultra, and I would get a stable 43 FPS with CF, but again, not as smooth as CF disabled.

Specs:

CPU: i5-4670K OC'd @ 4.4
MB: Asrock z87 Pro 4
Ram: 16GB G.Skill Cas10 @ 1600
GPU: HD-687A - ZNFC (main) & HD 687A - ZHFC (second) (same cards, different heatsink)
PSU: Corsair TX 850 M

Solution Tried:

I've tried 12.09, 12.10, and 13.10 beta version of CCC, with new catalyst profile.
I've disabled ULPS in registry & Trixx as well. (When I use other programs to disable ULPS, it gives me an error that the registry number cannot be found)
I've flashed the GPU Bios from Techpowered Up.
Took out the secondary card, put it in the primary slot, (works perfectly)

Benchmarks:

3dMark11 w/ CF: http://www.3dmark.com/3dm11/7179533
3dMark11 w/o CF: http://www.3dmark.com/3dm11/7174944
After burner

GPUz Cards ran at the same time:
Main Card:

Second Card:

GPUz cards ran separately (only card in the pcie)
1st card:

2nd card:

I noticed that my 2nd card's voltage is very high, even when idle. I flashed the bios, still the same.

Any help would be much appreciated.

Thanks You

thismafiaguy · Oct 7, 2013

Your motherboard isn't CrossFireX compatible. You've got one PCI-E 3.0 slot running x16 operation, but the other one is PCI-E 2.0 running x4 operation, which has much less bandwidth.

In CrossFireX, both cards are basically working together, so if one of them is severely handicapped by a low bandwidth interface, the other one is also held back because it has to "wait" for its partner, thus resulting in less overall performance.

asalikus · Oct 7, 2013

It's pretty simple, your motherboard runs one video card on a PCI express 3.0 x16 and the other is running on a PCI 2.0 x4. Some video games may not even support crossfire which in that case you won't even be able use both cards.

Matthew Share :

Hi guys

Problem:

My crossfired 6870's yields a worse performance than a single card. On all of the games I've played, I got the same problem. (League Of Legends, NBA 2k14, Crysis 2, DMC5, Grid 2, etc) For example In LoL, I would get a stable, non-stuttering 180 frames with CF disabled, but with CF I only get 80 and with a lot of stuttering. I turned it to the lowest setting, and I'm still getting the same low fps with CF disabled. With other games like NBA 2k14, I would get about the same FPS with CF both disabled and enabled, but it stutters a lot with CF enabled. I ran Crysis 2 on ultra, and I would get a stable 43 FPS with CF, but again, not as smooth as CF disabled.

Specs:

CPU: i5-4670K OC'd @ 4.4
MB: Asrock z87 Pro 4
Ram: 16GB G.Skill Cas10 @ 1600
GPU: HD-687A - ZNFC (main) & HD 687A - ZHFC (second) (same cards, different heatsink)
PSU: Corsair TX 850 M

Solution Tried:

I've tried 12.09, 12.10, and 13.10 beta version of CCC, with new catalyst profile.
I've disabled ULPS in registry & Trixx as well. (When I use other programs to disable ULPS, it gives me an error that the registry number cannot be found)
I've flashed the GPU Bios from Techpowered Up.
Took out the secondary card, put it in the primary slot, (works perfectly)

Benchmarks:

3dMark11 w/ CF: http://www.3dmark.com/3dm11/7179533
3dMark11 w/o CF: http://www.3dmark.com/3dm11/7174944
After burner

GPUz Cards ran at the same time:
Main Card:

Second Card:

GPUz cards ran separately (only card in the pcie)
1st card:

2nd card:

I noticed that my 2nd card's voltage is very high, even when idle. I flashed the bios, still the same.

Any help would be much appreciated.

Thanks You

Deleted member 217926 · Oct 7, 2013

Your motherboard isn't CrossFireX compatible. You've got one PCI-E 3.0 slot running x16 operation, but the other one is PCI-E 2.0 running x4 operation, which has much less bandwidth.

In CrossFireX, both cards are basically working together, so if one of them is severely handicapped by a low bandwidth interface, the other one is also held back because it has to "wait" for its partner, thus resulting in less overall performance.

^ That's it. 100%.

Matthew Share · Oct 7, 2013

thismafiaguy :

http://www.asrock.com/mb/Intel/Z87%20Pro4/?cat=Specifications

My motherboard does supports crossfire,but it does so at x16 / x4 (possibly (x8/x4?)

Even so, I should only loose about 3% using a 4x slot right?

edit : In this case, would you suggest, getting a new motherboard, or sell the cards and get a new card?

thismafiaguy · Oct 7, 2013

The more powerful your GPU is, the more performance you'll lose due to bandwidth restriction. With PCI-E 2.0 at x4 operation, you're losing a bit more than 3%, made obvious simply by comparing your benchmarks.

ASRock is going to say whatever it takes to sell the product, it's called marketing. That motherboard is technically compatible with CrossFireX, as in it can run two GPUs together. But by looking at the real-world performance, you see that it's not the whole story.

I would suggest selling the cards and get a single GPU. A multi-GPU set up can potentially give you a better performance/dollar ratio compared to a single more powerful card, but that's pretty much the only upside about multi-GPU configurations. You can take my word for it, I've been in your shoes before with dual 5850s.

AMD is about to release a new line of GPUs. I would suggest checking out the R9 270X or the R9 280X.

boju · Oct 7, 2013

states in the manual

1 x PCI Express 3.0 x16 slot (PCIE1: x16 mode)
•
1 x PCI Express 2.0 x16 slot (PCIE3: x4 mode)
•
If PCIE2 or PCIE4 slot is occupied, PCIE3 slot will run at x2

If theres anything inserted into pci slot's 2 and 4, the 3rd slot (used for gpu's) will be reduced again to x2 speeds -_- Way to go Asrock...

Matthew Share · Nov 5, 2013

I just got myself an asrock z87 killer fatal1ty. I just ran the test, and I got a lower performance.
http://www.3dmark.com/3dm11/7432916
this time it's x8, x8 config. Still don't know what's going on

potpolima · Nov 5, 2013

check your bios, sometimes pcie x4 is set to 2x by default...

iam2thecrowe · Nov 5, 2013

you have a crossfire bridge installed?
but really, i had 2 6850's in crossfire, while performing better in many games than a single card, it was not smooth, and the 1gb vram is a limitation for many recent games. Do yourself a favor and sell the cards, get a better single card with 2gb + vram. I found a single gtx660 to be smoother in games than 2 6850's despite the 6850's benching higher fps.

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