290x Crossfire Question

[Tandemclown]

Hi i recently posted a topic on this forum and got some great responses, the question was that i had low fps on my rig even with a 290x, it turned out it didn't have anything to do with the vram which was why i bought the card, the coreclock was the reason, i fired up msi afterburner and it showed that the Gpu was at 100% and that was what was "bottlenecking" my games, so my question is if i were to buy another 290x 8gb what kind of perfomance increase would i see? why am i asking? the motherbaord only have 1 pcie 3.0 16x slot and one pcie 2.0 16x but the website says if one were to use crossfire it would be running in 4x...

I just started overclocking the card and starting to get closer to the performance i would like but it just wont cut it....

Link to the old post: http://linustechtips...0x-8gb-low-fps/

My specs are:

Motherboard: Asus b85 Pro gamer

CPU: i5 4440

GPU: 290X 8GB

RAM: 8gb 1600 mhz

OS: Windows 8.1 pro

Any help is appreciated!

[Tim Drake]

What resolution is your monitor?

[Tandemclown]

I use eyefinity so it's with bezel correction at 6048x1080

[blu4]

You're most likely to see 80% scaling with two but the VRAM amounts will NOT add together, you are still stuck with 8GB.

[Godlygamer23]

The core clock is not the same as GPU usage.

[Tim Drake]

I use eyefinity so it's with bezel correction at 6048x1080

Please quote so I can see your reply

 

Em have you tried restarting? Sounds terrible but sometimes my GPU won't overclock from 540MHz and I get bottlenecked

[Tandemclown]

I have tried restarting, and I already knew about the vram being stuck at 8gb,but 80 % sounds acceptable, thanks for the answers!

[MEC-777]

@Tandemclown

 

There's nothing "wrong" with your 290x or your setup. You want to see 100% GPU usage (or close to it) and less than 90% CPU usage in demanding games. This is how you know your system is giving you the best performance it can. You want the CPU running below it's limits so that the GPU doesn't have to wait for instructions and can simply pump out the frames as fast as it can (at 100%). In any PC there will always be a bottleneck and with a gaming rig, you want that bottleneck to be the GPU.

 

With three 1080p displays in surround (eyefinity) you're driving 3 times the pixels of a single 1080p monitor. Depending on the game and graphics settings, that can be a lot for a single 290x to handle, so I'm not surprised to hear you're not getting the performance you want. Running two 290x's will definitely be a significant improvement in most games. Some games don't scale much at all with multi-GPUs and that's an issue with the game's optimization and/or a driver issue, but for the most part, you should see good performance scaling. 

 

With your setup, running eyefinity, you were smart to go with the 8GB 290x. You'll still only have 8GB total available with two 290x's, but that should still be more than enough.

[xAcid9]

Please don't CFX with that board, i tried crossfiring my 7950 over a year ago with PCIE 2.0 x8 + 2.0 x4 configuration and it did not run well. 

 

 

QUADFIRE!!!11!1...x1 speed.

[MEC-777]

Please don't CFX with that board, i tried crossfiring my 7950 over a year ago with PCIE 2.0 x8 + 2.0 x4 configuration and it did not run well. 

 

-snip-

 

QUADFIRE!!!11!1...x1 speed.

 

Yeah, that could be an issue. Good catch. I totally forgot to look at the OP's motherboard. PCIe 2.0 is half the lanes of PCIe 3.0. So while 3.0 at x4 would be ok, 2.0 at x4 is not (it's the equivalent of PCIe 3.0 at x2). It might be ok for two R9 270's but not two 290x's. 

 

In that case, @Tandemclown, you basically have two choices;

 

-Swap to another motherboard that has two PCIe 3.0 slots running at 16x/4x or 8x/4x or 8x/8x (8x/8x being the most ideal).

 

-Or keep your motherboard, hold off and wait for the R9 390X slated to be launched in a few weeks.

 

You can easily tell if a board has two 8x/8x PCIe 3.0 slots (when both are occupied) because it will have support for SLI.

[Godlygamer23]

Yeah, that could be an issue. Good catch. I totally forgot to look at the OP's motherboard. PCIe 2.0 is half the lanes of PCIe 3.0. So while 3.0 at x4 would be ok, 2.0 at x4 is not (it's the equivalent of PCIe 3.0 at x2). It might be ok for two R9 270's but not two 290x's.

In that case, @Tandemclown, you basically have two choices;

-Swap to another motherboard that has two PCIe 3.0 slots running at 16x/4x or 8x/4x or 8x/8x (8x/8x being the most ideal).

-Or keep your motherboard, hold off and wait for the R9 390X slated to be launched in a few weeks.

You can easily tell if a board has two 8x/8x PCIe 3.0 slots (when both are occupied) because it will have support for SLI.

No its not half the lanes. It's half the bandwidth. The number of lanes is the multiplier. For example, PCIe 2.0 x16 has the same number of lanes as PCIe 3.0 x16 because of the x16 multiplier. However, it has half the bandwidth.

[MEC-777]

No its not half the lanes. It's half the bandwidth. The number of lanes is the multiplier. For example, PCIe 2.0 x16 has the same number of lanes as PCIe 3.0 x16 because of the x16 multiplier. However, it has half the bandwidth.

 

You're right, it's bandwidth not lanes. My bad, thanks for the correction.

[AsGoodAsAHacker]

@Tandemclown

There's nothing "wrong" with your 290x or your setup. You want to see 100% GPU usage (or close to it) and less than 90% CPU usage in demanding games. This is how you know your system is giving you the best performance it can. You want the CPU running below it's limits so that the GPU doesn't have to wait for instructions and can simply pump out the frames as fast as it can (at 100%). In any PC there will always be a bottleneck and with a gaming rig, you want that bottleneck to be the GPU.

With three 1080p displays in surround (eyefinity) you're driving 3 times the pixels of a single 1080p monitor. Depending on the game and graphics settings, that can be a lot for a single 290x to handle, so I'm not surprised to hear you're not getting the performance you want. Running two 290x's will definitely be a significant improvement in most games. Some games don't scale much at all with multi-GPUs and that's an issue with the game's optimization and/or a driver issue, but for the most part, you should see good performance scaling.

With your setup, running eyefinity, you were smart to go with the 8GB 290x. You'll still only have 8GB total available with two 290x's, but that should still be more than enough.

This

[-iSynthesis]

2.0 x4 will most likely bottleneck a 290x.

[-iSynthesis]

Please don't CFX with that board, i tried crossfiring my 7950 over a year ago with PCIE 2.0 x8 + 2.0 x4 configuration and it did not run well. 

 

 

QUADFIRE!!!11!1...x1 speed.

Quadfire with 2xdual GPU cards. You cannot run a GPU in x1.