Low PPD with Crossfire [with 14.12 driver]

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Low PPD with Crossfire [with 14.12 driver]

Postby Silver_Pharaoh » Fri Jan 09, 2015 1:06 am

Hello again guys!

So after much fussing and messing with settings I got crossfire working perfectly. Great FPS in games now, BUT I have lost 60K+ PPD! :(
Disabling crossfire fixes this, and I am up to ~130K PPD.

I have noticed when I have Crossfire enabled, my GPU usage hovers around the low 70s to low 80s %, instead of the usual 99% usage.
The TPF on my 7850 also increases to ~27 minutes, and the 270x TPF is reduced to ~10 sometimes 5 minutes. :shock:

270x is in the top pcie x16 slot, 7850 in bottom pice x16 slot.
The only things I have changed recently was my CPU (got 3570K) and the 270x is now driving my monitor instead of a dummy plug. (7850 is not driving anything, no dummy plug, no monitor) and of course, I recently add the crossfire bridge and enabled it.
I have also set an application profile forcing crossfire off in CCC.
Lemme know if you need screenshots or a client log.

Running latest AMD drivers, 14.12 (non BETA)
MSI R7850 and Sapphire Dual-x 270x Both overclocked. 1180 core 1350 memory and 1150 core 1500 memory respectively.
I5 3570K @ 4.3Ghz folding on 2cores
Windows 7 x64

Any ideas as to why crossfire kills my TPF and PPD??
Silver_Pharaoh
 
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Re: Low PPD with Crossfire

Postby bruce » Fri Jan 09, 2015 4:00 am

It was my understanding that whether XF is enabled or disabled made no difference to FAH unless there's active processing of Video. FAH uses a single GPU whether or not XF is in use, so it takes two clients.

If this has changed, you're the first to report it.
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Re: Low PPD with Crossfire

Postby Silver_Pharaoh » Fri Jan 09, 2015 10:43 pm

bruce wrote:It was my understanding that whether XF is enabled or disabled made no difference to FAH unless there's active processing of Video. FAH uses a single GPU whether or not XF is in use, so it takes two clients.

If this has changed, you're the first to report it.


It hasn't changed.
If I fold on my CPU and 270x, the GPU usage on the 270x is 99% and the 78560 is at idle.

However folding on CPU + 270x +7850 I get ~70-80% usage on both GPU's if crossfire is enabled.
That's why I'm confused, why would the GPU usage drop like this?

It doesn't matter if I fold on the CPU at the same time or not, I still get lower GPU usages which = low PPD. :?
Silver_Pharaoh
 
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Re: Low PPD with Crossfire

Postby bruce » Sat Jan 10, 2015 2:59 am

Silver_Pharaoh wrote:It hasn't changed.
If I fold on my CPU and 270x, the GPU usage on the 270x is 99% and the 78560 is at idle.

However folding on CPU + 270x +7850 I get ~70-80% usage on both GPU's if crossfire is enabled.
That's why I'm confused, why would the GPU usage drop like this?

It doesn't matter if I fold on the CPU at the same time or not, I still get lower GPU usages which = low PPD. :?


Add a second GPU slot. You should be folding three different WUs concurrently. One on each GPU plus one on fewer than all of the CPUs.
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Re: Low PPD with Crossfire

Postby Silver_Pharaoh » Sat Jan 10, 2015 4:49 am

bruce wrote:
Silver_Pharaoh wrote:It hasn't changed.
If I fold on my CPU and 270x, the GPU usage on the 270x is 99% and the 78560 is at idle.

However folding on CPU + 270x +7850 I get ~70-80% usage on both GPU's if crossfire is enabled.
That's why I'm confused, why would the GPU usage drop like this?

It doesn't matter if I fold on the CPU at the same time or not, I still get lower GPU usages which = low PPD. :?


Add a second GPU slot. You should be folding three different WUs concurrently. One on each GPU plus one on fewer than all of the CPUs.


Exactly. And that's what I have been doing since I started folding last year :D
That's why I have no clue why this is happening. Somehow, folding on the 7850 with crossfire on affects the 270x's GPU usage which kills the PPD. At the same time the 270x then kills the 7850's GPU usage and it's PPD.
Silver_Pharaoh
 
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Re: Low PPD with Crossfire

Postby bruce » Sat Jan 10, 2015 5:41 am

Perhaps enabling XF causes the CPU service that supplies data to the GPUs are synchronized. The time to service a single wavefront varies both with the number of atoms and the speed of the GPU. [Identical GPUs running identical projects can be synchronized without loss.] Running in non XF mode would set up two CPU cores, each servicing one GPU, so they should work fine unless something tries to synchronize them.

I'm just guessing how they might have written XF, given your observations. Running a pair of non-identical GPUs in CrossFire has always been a bit dicey.
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Re: Low PPD with Crossfire

Postby Silver_Pharaoh » Sat Jan 10, 2015 2:06 pm

bruce wrote:Perhaps enabling XF causes the CPU service that supplies data to the GPUs are synchronized. The time to service a single wavefront varies both with the number of atoms and the speed of the GPU. [Identical GPUs running identical projects can be synchronized without loss.] Running in non XF mode would set up two CPU cores, each servicing one GPU, so they should work fine unless something tries to synchronize them.

I'm just guessing how they might have written XF, given your observations. Running a pair of non-identical GPUs in CrossFire has always been a bit dicey.


So then it sounds like crossfire is trying to synchronize my GPU's (as it should for games) but F@H is trying not to?
The only real solution is to always disable crossfire to resume folding?
Silver_Pharaoh
 
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Re: Low PPD with Crossfire

Postby Silver_Pharaoh » Sat Jan 10, 2015 5:56 pm

Okay! I have resolved the issue!

I downgraded back to AMD Catalyst drivers 14.9, and I now achieve ~128K PPD WITH crossfire enabled!
So it seems these "OMEGA" drivers are a bit buggy still. I hope they will fix this though.


So for those who find this thread with this issue, uninstall the AMD drivers, reboot in safe mode and run display driver uninstaller (3rd party clean up tool) and reboot again, install AMD Catalyst 14.9 drivers, reboot and you should be good to go! :D
Silver_Pharaoh
 
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Re: Low PPD with Crossfire [with 14.12 driver]

Postby foldy » Mon Jan 26, 2015 7:07 pm

I also did a crossfire setup with 2x HD7950 now and configured with 2 gpu slots.
I use the 14.12 driver but did the 14.9 OpenCL workaround mentioned in my other thread to prevent performance problem.
viewtopic.php?f=81&t=27115#p272345
I had to disable video HW acceleration to prevent freeze and driver crash, e.g. in Silverlight Video Streams.
Now it works like a charm :-)
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Re: Low PPD with Crossfire [with 14.12 driver]

Postby Silver_Pharaoh » Sun Feb 01, 2015 3:42 pm

foldy wrote:I also did a crossfire setup with 2x HD7950 now and configured with 2 gpu slots.
I use the 14.12 driver but did the 14.9 OpenCL workaround mentioned in my other thread to prevent performance problem.
viewtopic.php?f=81&t=27115#p272345
I had to disable video HW acceleration to prevent freeze and driver crash, e.g. in Silverlight Video Streams.
Now it works like a charm :-)


Thanks! I will keep this in mind when I update back to 14.12. 8-)
Disable HW acceleration, in the browser or somewhere else?
Silver_Pharaoh
 
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Re: Low PPD with Crossfire [with 14.12 driver]

Postby bruce » Sun Feb 01, 2015 9:34 pm

Hardware acceleration (or the equivalent, called by a different name) can generally be disabled in browsers, operating systems, video player/decoders, etc. etc. -- anything that uses the display.

Before GPUs were developed that could actually do a lot of computations, everything was handled by the CPU other than the actual movement of information from some kind of memory to the display. The CPU can still be used for those activities. Generally, the system designers ASSUME that if you have a GPU, it is expected to powerful, computationally speaking, and to be mostly idle. When your GPU is folding, that assumption is false and, in fact, the CPU is often idle when a screen refresh needs to be processed and quite capable of doing the computations necessary to process the screen image fast enough that you don't perceive a delay..
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