6990 + 6970 Tri-fire w/ 1x16 PCIe and 1x4PCIe slot...

[jedbot5000]

Will the second x4 PCIe slot severely cripple the scaling for the tri-fire? After I put in the 5970 I hardly notice any difference with FPS in Crysis 2...was hoping for a little more than nothing. I've got an Asus P8P67 16 Gigs of DDR3 1600Mhz, and an i7 2600k @3.4Ghz. Should I return that board and get one with 2 x16 PCIe slots? Would it make that big of a difference??

 

[simon12]

Yes the 4x slot will cripple the 6970 (I Assume the 5970 is a typo) as for how much difference it will make I have no idea how well this kind of setup will scale.

 

[alikum]

You don't necessarily need 2 x16 although it's good to have. 2 x8 is good enough in your case. What resolution are you playing at? Do you really need that much power?

 

[Lmeow]

I'm assuming you're running one HD 6990 in the PCI-E x16 slot, and the HD 6970 in the PCI-E x4. Normally, a setup like that wouldn't be bottlenecked seeing as the PCI-E x4 (2.0, based on ASUS' website) is more then sufficient to provide close to enough bandwidth for the HD 6970. On their website however, it does say 'the PCIEX16_2 slot shares bandwidth with the PCIEX1_1 slot, PCIEX1_2 slot and USB3_34 connector. The PCIEX16_2 runs at x1 mode by default for system resource optimization.' I'm assuming that if you have any of them active, the PCI-E x16 slot will run at x1 which would cause your problem. Is Crysis 2 the only game you've tested? See if any other games scale differently with and without the HD 6970.

 

[cburke82]

Also if you look at the scaing tests that toms did here you will see that a third card does not scale as well. So one card gets you 40fps the second might get you 70 and the third 80. Somethings like that for exact numbers just look up the test here. I myself read that article and found myself thinking that 3 cards was not worth it at all. Then add the fact that they did that with 3 seperate cards. They tested the 6990 and it is a bit slower than 2 6970's. So I would think if the 6990 is slower than 2 6970's then using the 6990 with a 6970 would be slower than 3X6970. This may be off but I think you should look into that.

 

[jedbot5000]

Ha...whooops! Yeah thanks for pointing that out.

Yes the 4x slot will cripple the 6970 (I Assume the 5970 is a typo) as for how much difference it will make I have no idea how well this kind of setup will scale.

 

[jedbot5000]

On this setup I'm running 5760x1200 on three 27" monitors...so unnecessary but I guess that's kind of the point here. I think I'm going to get a board that supports at least a second x8 slot instead of x4...If I spent the money on these cards I want to get every last ounce I can out of them. Would I notice much of a difference overclocking the i7 2600k from 3.4 to 4+? And would I need to overclock the DDR3 ram from 1600 to 1800 or more? Again...would that make much of a difference in the FPS? I'm right at the verge of it running at acceptable levels....so minor tweaks might just make the difference I'm looking for. Thanks again for all the replies.

 

[cburke82]

On this setup I'm running 5760x1200 on three 27" monitors...so unnecessary but I guess that's kind of the point here. I think I'm going to get a board that supports at least a second x8 slot instead of x4...If I spent the money on these cards I want to get every last ounce I can out of them. Would I notice much of a difference overclocking the i7 2600k from 3.4 to 4+? And would I need to overclock the DDR3 ram from 1600 to 1800 or more? Again...would that make much of a difference in the FPS? I'm right at the verge of it running at acceptable levels....so minor tweaks might just make the difference I'm looking for. Thanks again for all the replies.

Dont know if you did already or not. But again I would suggest looking at some tri fire scaling benchmarks. There isnt that much more performance to be had by adding the 3rd card. Could you possibly get fraps and do some real benchmarks? Basicly if you are getting 60 with the 6990 by itself and then 70-75 with the third card, you might find spending money on a new mobo wont get you much. It doesnt double every card you add it wount go 40>>80>>120 it will go closer to 40>>70>>80. So if your going to go spend say $100-$150 on a new mobo (possibly more??) Yu might fing that the lack of an increase in FPS is due more to scaling issues and not the PCI slot.

PS: If i totally missed something and you did do benchmarks and ar geting numbers that are exactly the same my bad. Also try getting GPU-Z and checking to see if the second card is even being used before you get another mobo.