PCI-E x16 and PCI-E x16 running at x4 Crossfire setup with R9 270

spacecadet01 · Sep 19, 2014

I intend to upgrade my video card from a GTX 460 to a R9 270 and eventually crossfire it with 2 of them.
My mobo is Gigabyte G1.Sniper B5
http://www.gigabyte.com/products/product-page.aspx?pid=4594#ov

The second PCI-E slot is running at x4 speed and from what I hear that is not ideal for crossfire or sli.

My question is ...How much of a performance hit will I take doing this (average FPS loss examples welcome). I have heard there is only a slight loss in performance.

I have never had a dual video card setup and am excited to try it. Will it be worth it?

Thank you in advance

- Pete

clutchc · Sep 19, 2014

It varies from card to card and from MB to MB. It will also vary from game to game and PCI3 2.0 and 3.0. So it is not possible to give an exact number. But from my experience with a X16, x4 MB, it wasn't pretty. Some games even lost a few fps compared to using just the single card. But that was back in the HD 6xxx days. The higher performance the card, the more it will suffer. The 2 x R9-270s would be about in the class my 2 x HD 6xxx cards were, so I would expect the same results.

VincentP · Sep 19, 2014

Here is a benchmark showing scaling with the different PCI-E bandwidth options:
http://www.techpowerup.com/reviews/Intel/Ivy_Bridge_PCI-Express_Scaling/15.html

The whole article is about PCI-E scaling.
Have a look at the HD 7970 results as these will give you an idea of the impact on the second card.
In Crossfire, the first card will have to slow to match the second card as they are rendering alternate frames.

The second slot supports PCI-E 2.0 x4 compared to PCI-E 3.0 x16 for the first slot.
If we look at the 1920x1080 benchmark for the HD 7970:
PCI-E 3.0 x8 or x16 score 33.9 FPS
PCI-E 3.0 x4 or PCI-E 2.0 x8 scores 33.4
PCI-E 2.0 x4 scores 32.6

This is only a 4% drop in performance so not such a big deal.

Keep in mind though that crossfire or SLI only add about 60% performance to that of a single card, and not all games support it.
The R9 270 also only has 2GB of VRAM which will limit it in high resolutions or detail settings, and crossfire or SLI does not help with this.
If you are happy with medium to high settings at 1920x1080 then the R9 270 is fine.
If you want better settings, you should choose a better card rather than considering crossfire.
Have a look at the R9 290 or GTX 970.
Expect price drops across the range in the next few weeks too with the release of the GTX 970 and 980 today.

This should give you an idea of R9 270 performance:
http://www.guru3d.com/articles_pages/amd_radeon_r9_270_review,22.html
The new GTX 970 will perform better than the R9 290.

The Original Agrajag · Sep 19, 2014

^this. In your situation your better off saving your doubloons for a 280/290 or 770/780. That way your performance boost is guaranteed and you won't run the risk of micro stuttering from two cards communicating from different rated PCI-e slots.

spacecadet01 · Sep 19, 2014

The Original Agrajag :

You're probably right...I didn't know it wouldn't work in every game...don't know what micro stuttering is but it sounds like it would be annoying...bummer ...I was excited about this too...
Oh well

The Original Agrajag · Sep 19, 2014

For only a few extra pennies you can get a 280 or a 770 that will eat most games for breakfast on its own. Remember you can always save for a new MOBO in the future that will better support crossfire/sli.

VincentP · Sep 20, 2014

His motherboard isn't the problem in using crossfire, this issue is that the performance benefit you get from crossfire or SLI is not worthwhile in the vast majority of situations.

The Original Agrajag · Sep 20, 2014

Surely running sli in duel PCI-e 3.0 would be better than the OP's situation? I must admit I've never tried personally because I simply prefer single GPU setups rather than multi-gpu.

VincentP · Sep 20, 2014

The Original Agrajag :

I posted the benchmarks. The performance difference is about 4%. This is the least of your problems with crossfire or SLI.

spacecadet01 · Sep 20, 2014

VincentP :

Thanks for this. I didn't quite understand your post and the information in the link at first but upon reading your post again I get what you're saying. I was aware of the 60% thing but I didn't know that crossfire and sli are not 100% compatible with everything.

I had always been a fan of single card setups and after hearing all this I am back to the single card mentality. I have decided to save up for a GTX 970.

Thanks

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PCI-E x16 and PCI-E x16 running at x4 Crossfire setup with R9 270

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