R9 290 3way crossfire vs 2x 7990 4K

hoorhay

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Sep 9, 2014
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As the title sloppily asks, which is better for 4K overall?

My friend and I are looking to build a semi-retro tower for 4K gaming to put in our repair shop. It'll be there for Ooooh's and Aaahhh's. So far we've go this going for us

CPU: Intel Core i7-3820 3.6GHz Quad-Core Processor
CPU Cooler: CRYORIG R1 Ultimate 76.0 CFM CPU Cooler
Motherboard: Asus Rampage IV Gene Micro ATX LGA2011 Motherboard
Memory: G.Skill Ripjaws X Series 8GB (2 x 4GB) DDR3-1866 Memory
Storage: Crucial MX100 512GB 2.5" Solid State Drive
Case: Corsair 750D ATX Full Tower Case
Power Supply: Corsair Enthusiast 750W 80+ Certified ATX Power Supply
Operating System: Microsoft Windows 10 Home OEM (64-bit)

Some is new, some is obviously used. We're not looking for suggestions elsewhere in the build. It's used from what we had available/could afford. We have 2x 7990 on hand, as well as 1x ASUS DirectCUii R9 290. We could grab 2x more of the identical 290's for $150 even from a customer that's upgrading his hardware.

Which do you think would drive a 4K monitor better with details turned up graciously? Leaning towards the 290's due to a less severe minimum frame rate from vram throttle. But not sure. And yes, we know we have to swap out the power supply. The tx750 was chosen when we were just planning to use a single 7990.
 
Solution


I agree on this. Save the money for the last 290, and add watercooling and overclock the 2x 290. You will be better off with this.

Easy watercooling: Corsair HG10 A1 bracket + AIO watercooling

SBargisen

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Jul 15, 2015
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Well... The 7990 is equal to 280x crossfire, except for clocks maybe. The 290 is better than the 280x, clearly.

So 3x 290 will beat 4x 280x or 2x7990. And here we aren't talking about compatibility for games with trifire vs quadfire, though trifire probably works better than quadfire.


Secondly, you get worse and worse scaling the more gpus you match. single gpu (100%) -> Crossfire (190%) -> Trifire (270% -> Quadfire (350%)
Ofcourse, these percentages aren't true in anyway, they are just made up numbers from my head, but only there to give you an idea of increase in performance, and remember that it will only increase like this: 90% more performance with crossfire vs single card, 42% from cross to tri and 29% from tri to quad. Even this is being optimistic.

I strongly believe trifire 290 will be best. But honestly. You need a 1200w+ powersupply either way. trifire 290 = 275x3 watts (TDP) and also add fluctuations etc. It might use more in "spikes" so better be prepared.

The 7990 in quadfire setup will use 2x375w in total, + what I wrote before.
 

SBargisen

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Jul 15, 2015
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I agree on this. Save the money for the last 290, and add watercooling and overclock the 2x 290. You will be better off with this.

Easy watercooling: Corsair HG10 A1 bracket + AIO watercooling
 
Solution