7950 crossfire issues

Djentleman · Jun 6, 2013

Hello.

I just got a second card for crossfire today. And i've been getting odd performance.
One thing that's odd is my gpu usage. I'll have one card that is at 73% and the other at 100%. I don't know if this is normal or if it's rivatuner glitching.
I also only got a 10 fps improvement in crysis 3, and it's choppy at that. Although i run the multiplayer now at 60fps with msaa @4 on very high.

I'll try to post a video in a bit.

Specs:
3570k @4.4
8gb of ram
2x 7950's

Darkman69 · Jun 6, 2013

BigMack70 :

Would Vsync work ?

Darkman69 · Jun 6, 2013

BigMack70 :

I think Vsync would suffice. It does for me.

bystander · Jun 6, 2013

One issue with v-sync, is if you don't maintain your refresh rate, it can cause additional stuttering due to the nature of having to wait on vertical retrace mode, which will alternate frame times.

Darkman69 · Jun 6, 2013

bystander :

Not really but it does add negligible mouse input lag.

bystander · Jun 7, 2013

Darkman69 :

Yes really. V-sync doesn't let you write except during vertical retrace. That means it cannot have evenly distributed frames. With a 60hz monitor, that means at 45 FPS, you'll have alternating frame times of 16.7ms and 33.3ms. That causes a bit of stuttering.
http://www.pcper.com/reviews/Graphics-Cards/Frame-Rating-Dissected-Full-Details-Capture-based-Graphics-Performance-Tes-11

I notice it when I use 3D Vision, because vsync is forced on. If my FPS do not maintain 60, it stutters. The same thing happens with normal 2D on 60hz monitors. It is less noticeable on 120hz monitors due to the extra refresh time interval.

Darkman69 · Jun 7, 2013

bystander :

Darkman69 :

Yes really.

Cite your sources... Vsync inhibits inherent mouse input lag but thats it ....

bystander · Jun 7, 2013

Darkman69 :

I did on the post you just quoted. Click the link.

Here is a better one that is specifically talking about the stuttering:
http://www.pcper.com/reviews/Graphics-Cards/Frame-Rating-Visual-Effects-Vsync-Gaming-Animation

The single card and SLI configurations without Vsync disabled look just like they did on previous pages but the graph for GTX 680 SLI with Vsync on is very different. Frame times are only switching back and forth between 16 ms and 33 ms, 60 and 30 instantaneous FPS due to the restrictions of Vsync. What might not be obvious at first is that the constant shifting back and forth between these two rates (two refresh cycles with one frame, one refresh cycle with one frame) can actually cause more stuttering and animation inconsistencies than would otherwise appear.

Darkman69 · Jun 7, 2013

bystander :

Um seems frame times are not the issue here cite some other source to bacj up your claims because we are not buying it !

bystander · Jun 7, 2013

Darkman69 :

It says almost word for word what I said. What more do you want?

http://www.pcper.com/reviews/Graphics-Cards/Frame-Rating-Visual-Effects-Vsync-Gaming-Animation

Frame times are only switching back and forth between 16 ms and 33 ms, 60 and 30 instantaneous FPS due to the restrictions of Vsync.

What might not be obvious at first is that the constant shifting back and forth between these two rates (two refresh cycles with one frame, one refresh cycle with one frame) can actually cause more stuttering and animation inconsistencies than would otherwise appear.

Read the whole article. It even has videos to watch so you can see for yourself. Read the comments. Look at the graphics:

Djentleman · Jun 7, 2013

BigMack70 :

I hope this is true. Although, it seems to happen to me in metro too.

Here's a pic of the gpu usage. Freggin' weird.

Djentleman · Jun 7, 2013

Also, i had the power limiter set in sapphire to 20+. I don't know why it wasn't showing in MSI.

bystander · Jun 7, 2013

As BigMack said, use a frame limiter. Not power limiter. The frame limiter or FPS limiter can force frames to space out avoiding microstutter. Though the GPU usage may still do like it is, but that isn't an issue if the stutter goes away.

Djentleman · Jun 7, 2013

bystander :

No more stutter since i've been using the frame limiter. I just thought the gpu usage was very odd; frame limiter or no frame limiter.

Mousemonkey · Jun 7, 2013

Don't...

Bump posts

http://www.tomshardware.com/forum/283384-33-read-first

bystander · Jun 7, 2013

Djentleman :

The FPS limiter causes the GPU to not need full power, so it is bouncing around as it is needed or being forced to wait. It does look interesting in the way that it happens, in that it is allowed to go full speed, then stop, then full speed and stop, but that is what a limiter does.

Djentleman · Jun 8, 2013

So i've discovered that my new 7950 that i got for crossfire is throttling with even the slightest overclock.
If it's anything above 850 core clock it throttles. This is only with my new one. It will hop between 64% and 100%, while my other one stays at average clocks. The only thing it doesn't do it in is heaven bench and BF3.
Is there any way to remedy this?

First one is a sapphire 7950 BOOST, and the other one is a XFX core edition.
Any help would be appreciated.

bystander · Jun 8, 2013

Djentleman :

Can you test them individually, with only one in the computer at a time? Your PSU might not have enough power to keep both going under full load when OC'ed. Testing them individually will narrow things down to whether it could be that or just the GPU itself.

Djentleman · Jun 8, 2013

bystander :

I turned off crossfire and used the XFX by itself and it still did this. 63 - 100%
The fps doesn't seem to change though, which is the odd thing.
I overclocked it to 1000mhz. I felt that it was a healthy overlcock.

bystander · Jun 8, 2013

Did you have v-sync on or a FPS limiter on during your test? Make sure both are off or it doesn't help us learn anything.

Djentleman · Jun 8, 2013

bystander :

Nope, i don't.

Djentleman · Jun 8, 2013

I can post a screen shot of the GPU usage and the fps, if it would help.

bystander · Jun 8, 2013

So the FPS was the same as the other card, or the FPS didn't change with the OC? If the other card at the same clock gets better scores, that one may not be performing well. You might also change how much power it can use by sliding the slider from 100% to 120% or higher.

If it performs at stock settings without problems, you may just have gotten unlucky with a bit of a dude OCer, which is not something you can do anything about.

You also want to test the card in both PCIe slots, to make sure it is not something going on with the PCIe slot. And again, make sure it is the only card in the machine.

Djentleman · Jun 9, 2013

bystander :

Okay, so i took at the other card and just kept the problematic one.
I fired up crysis 3 and this is what i got:

This is with 20% power limiter and at 65c.

It does it in bioshock too, but it's not as prevalent:

bystander :

The funny thing is, that the stock is 900 mhz, but even at that clock speed it gets wonky with the usage. Only at 850 is it normal. I asked the previous owner, and he said he didn't have a problem. (this is ebay mind you). Which he has a very good record so i wouldn't deny it.

I think i have plenty of power too. Considering i used killawatt and it wasn't even close to pulling 600 watts out of the wall. (this is with crossfire). Edit: It was averaging around 520w.

I also had the card in different slots, but it didn't work.

bystander · Jun 9, 2013

Crysis 3 is not a good choice to use, as it gets CPU bottlenecked often. What does it look like using an Unigine benchmark, like heavy or valley? If you are being CPU bottlenecked, you can expect some GPU usage drops, though you'd normally see it stay at less erratic %'s.

And if you could, run the same benchmarks with the other card, while using the same clocks. I'm curious if it is a sensor thing, or if you have different performances as a result.

7950 crossfire issues

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