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2 ATI HD Radeon 6990's In Crossfire Experienced Experts Only

post #1 of 56
Thread Starter 
OK I need some REAL EXPERT EXPERIENCED Information on Getting rid of the Bottlenecks these 2 baby's cause.
Please tell me exactly what my CPU clocks have to be.

Please look at my system specs, but disregard the CPU!!
I will be replacing it for either the fastest Freakin INTEL money can buy or the new AMD bulldozer when it arrives.

Also I am currently buying the stuff for my extreme watercooling setup.
so it will be watercooled, and the GPU's aswell.

Please only experienced people. I want the info from people that have actually had HD 6990's in crossfire and delt with bottlenecks and fixed it.

Thank you.
post #2 of 56
Having your title in all caps isn't going to bring your thread more attention -.-

You can eliminate your bottleneck by overclocking your current CPU to the mid-high 3 GHz range. I don't think it's reasonable to buy a new CPU just for that.
post #3 of 56
CPU speed, BCLK and RAM speed are the thing making the biggest difference in my experience. And watercooling. Don't expect crazy OC on air.

x16 vs x8 doesn't really make a major difference.

The best thing to do is to flash the BIOS of the 6990s to 1.25v, OC trough CCC (and not using Afterburner). But if you go to 1.25v, you need to watercool those cards.

An i7 2600K at 5.3-5.4 with an Asus Maximus IV, with RAM OC to DDR3-2133 or DDR3-2400 with tight timings will give you great results for a good price.

If money is burning a hole in your pocket, then a 980/990 plus a great X58 motherboard, with a high BCLK is also another great/crazy fast alternative... but it will cost you dearly. And Bulldozer, SB-E are near... so X58 is not the wisest choice right now.

Personnally, I would wait for Bulldoze and SB-E. And until then, start planning and building a good watercolling system, that will follow your upgrade path trough the years..
    
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i7-5930k @ 4.9  i7-3930k @ 5.1 (2nd rig) Asus Rampage V (X99) + Asus Rampage IV (2nd rig) 2X Nvidia 1080 Ti SLI watercooled 
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Samsung 850 Pro 250GB 3XSeagate 3TB LG Blu-ray writer 2X Quad-120 MCR420 
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2X EK Supreme HF CPU waterblock Windows 10 Pro x64 Acer XB270HU IPS G-Sync 2440p (main rig) 3X 30'... CoolerMaster Masterkeys Pro S MX blue switch, C... 
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i7-5930k @ 4.9  i7-3930k @ 5.1 (2nd rig) Asus Rampage V (X99) + Asus Rampage IV (2nd rig) 2X Nvidia 1080 Ti SLI watercooled 
GraphicsRAMRAMHard Drive
2X Nvidia 980 Ti SLI watercooled (2nd rig)  4X8GB=32GB G.Skill DDR4-2700 4X4GB=16GB Ripjaws DDR3 2400 CL9 (2nd rig) 3X Samsung 840 Evo 1TB SSD 
Hard DriveHard DriveOptical DriveCooling
Samsung 850 Pro 250GB 3XSeagate 3TB LG Blu-ray writer 2X Quad-120 MCR420 
CoolingCoolingCoolingCooling
2X Triple-120 MCR320 + 1X Triple-120 Feser 2X Dual-120 XSPC RX240 32 Gentle Typhoon fans (mix of 3000 and 1850rpm) Reservoir 2X Koolance RP-452x2 with 4X MCP655 p... 
CoolingOSMonitorKeyboard
2X EK Supreme HF CPU waterblock Windows 10 Pro x64 Acer XB270HU IPS G-Sync 2440p (main rig) 3X 30'... CoolerMaster Masterkeys Pro S MX blue switch, C... 
PowerCaseMouseAudio
Antec HCP1200 + AX850 dual PSU main rig, AX120... Mountain Mods Extended Ascension + Pedestal 24 ... Logitech G502 x 2 PSB speakers 5.1 
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post #4 of 56
your phenom II should be fine, like kiwiasian stated, you really should overclock your processor a bit and you will see ample improvement
Sharkbait
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Sharkbait
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post #5 of 56
If you do upgrade, a good 2500K will suffice. Don't go get a 990X for 1000 dollars and think its necessary.
post #6 of 56
Your CPU is bottlenecking even one 6990. I don't think BD will change that. You need all CPU power you can get, so 2600K is a logical solution
post #7 of 56
...just OC as much as you can while keeping the temps down. There is no magic CPU clock speed that will remove the bottle neck. It likely will always be there, but you can reduce it some by overclocking. You sound like you have at least a rudamentary knowledge of overclocking at least. If not there are a lot of guides out there.

Find the max and if for whatever reason you don't think you need it 24/7 or if the temps are too high for your comfort level just back down some.

You could try disabling two cores in the X6 to get some more MHz of it as well. Currently a quad core is all that is needed for gaming.
Edited by Vagrant Storm - 10/4/11 at 7:31am
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My System
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post #8 of 56
Even at 4.2ghz you are going to see a bottleneck. I see one with crossfire 6970s @ 950/1450 unless I go up to 4.42ghz. Now with the x6 being better at driving crossfire arangements, I still do not see it being able to properly drive a quadfire setup. To date all I have seen with quadfire (and not bottleneck) were highly overclocked 1366 i7s (4.2ghz+) including the hexcore models or SB chips running 5ghz.

Now for memory, that is not going to effect you nearly as much as you would think. Give your SB 1600 or up and you will see flawless performance.

For cooling of the GPUs, Water is not even a question. The only other option is a new Artic Cooler 6990 model. But for $150 a pop, go water. If you pick stock air, do not expect great overclocks unless you run your jet engine at 100%.

Comes down to quadfire is just a load of power. With so much power, it requires a much faster cpu to feed it. Without a faster CPU, it would be like racing a go-kart with jet fuel vs F1 car. Sure you have one half of the puzzle, but the other is just not enough.
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post #9 of 56
The only thing you will be able to do with your /current/ processor is take it to 4Ghz to relieve some of the pressure on it. Then your going to need to go with an SB proc, such as the 2500k or 2600k.
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post #10 of 56
Your CPU is the only bottleneck in the system.

I have similar experience with my setup, even though it's not quad sli, 1090T @ 4.3 bottlenecks 2x 6970 in mostly all apps(benchmarks/games)

May aswell get a 2500k/2600k and oc it to 4.5-5.0 and that will remove a good portion if not all of the bottleneck.

I myself have new intel stuff on the way.
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