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Interesting observation about 6990s

pcm81

Senior member
Mar 11, 2011
555
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I benched 2x6990s in 3dMark11 and here are the results:
980X @ stock (26 multiplier)
X3249 no CF
X3715 Enabled CF

980X @ multiplier 28
X3252 no CF
X5475 Enabled CF

980X @ multiplier 29
X4808 Enabled CF

went back down to multiplier 28 still get 4800 ish.

Looking at GPU-Z the main cards clock is at 550MHz. Two of my cards are near each other, so main cards air intake is effected. In all cases the 6990s are at stock clocks/volts

Conclusion:
1. 980X at stock speed holds back 2x6990s
2. 6990s if installed near each other will heat up and throttle down, which means water cooling should yield big improvements in long term performance, preventing the cards clocking lower than they start off with...

Not going to do any voltage mods to cards/cpu while on air.

I did notice earlier that i sometimes get X3000 with single card and X3300 with xfire, it now makes sense... those low score runs in the past must have been with "hot" slowed down cards.
 

Kenmitch

Diamond Member
Oct 10, 1999
8,502
2,244
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So what your saying is a stock 980X only has enough balls to drive a single 6990 in other words!
 

pcm81

Senior member
Mar 11, 2011
555
2
81
So what your saying is a stock 980X only has enough balls to drive a single 6990 in other words!
Pretty much. Also, if you using 2 6990s use water or don't put then in slots near each other, if possible.
 

Dadofamunky

Platinum Member
Jan 4, 2005
2,184
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LOL. Get a 2600K.

Well, that probably wouldn't be enough either. A crackup that a $1000 CPU isn't enough to push two 6990s. However, at least you know that the rig will still make Crysis 2 beg for mercy!
 
Feb 19, 2009
10,457
5
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Yeah the air intake design is bad for close position CF. Plus, it doesn't help you have a crazy ambient of 80F. :D You can afford 2x 6990, you can afford some aircond. No civilized person should live in that condition.
 

Kenmitch

Diamond Member
Oct 10, 1999
8,502
2,244
136
Once you get your water blocks on the only throttle you'll see is wide open :D
 

pcm81

Senior member
Mar 11, 2011
555
2
81
Yeah the air intake design is bad for close position CF. Plus, it doesn't help you have a crazy ambient of 80F. :D You can afford 2x 6990, you can afford some aircond. No civilized person should live in that condition.
I like it this warm... I have A/C...
 

pcm81

Senior member
Mar 11, 2011
555
2
81
Here are the results of this mornings test. I ran 6990s in CF right after the system restart, pc was off all night, so cards were cool.

980X clocked at 28 multiplier (stock is 26)
1. x5079
2. x3810
3. x3230
4. x3788
5. x3789

What we see is the cards perform well for the 1st test, become very hot, throttle way down for 3rd test and then stabilize at about X3788.

I have seen 3DMv11 scores as high as 5400 on this same system... Dot know why fresh start was not at 5400...

Both cards are at stock clocks of 830MHz.
 
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