Is it true that strong CPU is need in multi-GPU setup ?

[Enterprise24]

for 290X / 780 ti 4ways CF/SLI
need strong CPU in singlethread or multithread or both ?
Really need 3930K/4930K ?
Some game not scale well with cores like DX9 games or some bad optimize game or if game cannot use more than 4 core anyway (like most today game ) , in this type of game 4930K still better than 4670K ?
And if monitor is 3 x Ultra HD Resolution then bottleneck will ship from CPU to GPU or not ?

Sorry for my bad English , not my native language , thanks in advance

 

[buildzoid]

A 4670K will run 2 GPUs just fine if you're pushing a massive resolution.

 

[RCoon]

The scaling on 4 way sli/crossfire is awful, and for DX9 games, it's almost not worth attempting to pull off. Besides that, for 3 or more cards of any type, a x770K is practically required to get the best potential from that many cards.
If it were just two cards pushing a silly high res, like buildzoid said, standard i5 quad core would do the job. For more extreme instances, it's almost certainly worth 4C/8T or straight 6-8C.

 

[Jetster]

for 290X / 780 ti 4ways CF/SLI you really need the extra PCI-E lanes of a 2011 board

Games are starting to use more cores now too

 

[64K]

As Rcoon said 4 cards in SLI /Crossfire is a waste. The sweet spot is 2 cards for the best scaling. A third card adds more performance in total but not as much as the second card added as far as overall performance and a fourth card doesn't add enough performance to be worth it unless you absolutely need just a few more FPS to game. Drivers aren't optimized for 4 way SLI/Crossfire because so few people even have such a setup.

Going from your specs I see that your monitor is a 30 Hz Ultra HD. If you are going to try to run 3 of those at 30 Hz then you may be alright with just two GTX 780Ti or R9 290x cards since anything over 30 FPS would just be wasted anyway. If it were me I would try two of the above cards and see how it goes. You can always add a third card later.


Edit: I didn't even think about this until after I logged out but 3GB or 4GB of VRAM may not be enough for 3 Ultra HD monitors. 6 GB might be where you need to aim. The setup you're talking about is pretty exotic for right now.

 

[Enterprise24]

I have another question my monitor use DVI port to get 4K @ 30Hz (overclocked from 1440p to 4K by CRU).
My monitor support HDMI 1.4a so it cannot take advantage of HDMI 2.0 (4K @ 60Hz)
But if I use displayport 1.2 will it do 4K @ 60Hz ?

Currently I play game in 2 mode 1440p @ 120Hz for racing / adventure game , 4K @ 30Hz for strategy game (since RTS don't need 60FPS anyway).
Single 290X is not enough , I will buy another 290 or 290X in the end of this month.

But if my monitor can do 4K 60Hz via display port maybe I need tri-fire 290/290X.

 

[buildzoid]

For tri fire I would use 2 r9 290xs and 1 r9 290 to save some money. With tri fire you will need more pcie lanes so I7 4820k would be the best choice.

 

[GhostRyder]

I ran a 4 GPU setup multiple times and just recently went back to a 3 GPU setup with 290X cards. It is the best in my book for maximum performance and while keeping components worthwhile. In all cases the 4th GPU scales off pretty bad though AMD cards do the best job on the 3rd and fourth GPU (not by much mind you). I would not go higher than 3 cards though personally anymore.

 

[Aquinus]

Higher resolution puts more demand on your GPU(s) and less on the CPU. At higher frame rates, the CPU needs to do more work but at high resolutions since you're not going nuts with the frame rate, most CPUs will work fine depending on the game.

 

[Enterprise24]

Now I can do 4K 60Hz and further overclock 4670K to 5Ghz (1.4V) to prevent bottleneck as much as possible.
I See bottleneck in GRID 2 when play 2560 x 1440 @ 120Hz my 2nd gpu sometime work 100% but sometime not. Especially when the race has many AI. CPU usage is very high on all 4 cores nearly 90%.
But when switching to 3840 x 2160 @ 60Hz CPU usage on all core drop to around 50% and my VGA work 100% both.

 

[PHaS3]

from my side... I had a Phenom II 1100T @ 4.2GHz, and I felt little difference when I was forced to upgrade to my core i5 3570K @ 4.5GHz. It really depends on what you're playing, as with 2x 5850s it didn't matter in for e.g.. StarCraft2 as its really CPU dependent, whereas other games may favour more cores vs IPC even with dual cards. Currently I couldn't be happier with my single 680 and oc'd 3570K in all games, but come year end I will upgrade my graphics card regardless to a 290X or 780Ti (depending on what is available at the time).

As an aside, I noticed more difference going from my dual 5850s to single 680 than I did going from Phenom II to Core i5, bearing in mind I had my 680 with my Phenom II before my Intel CPU. I do only game @ 1080p though.