Overclocking Crossfire

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1Kurgan1

New Member
My current setup is listed in my sig. I did have a 2nd 3870 till my gf's old x1950Pro gave out so I gave one to her and ordered another 3870.

To start it off here were my 3dmark06 scores with Vista 64.

5000+ @ stock - 1x 3870 @ stock = 8872
5000+ @ 3.0Ghz - 1x 3870 @ 876/1254 = 9812 (nice increase)
Just to note a long time ago I had broken the 10k mark in 3d06 with a much lower OC on the videocard and no OC on the processor.

Now onto crossfire.

5000+ @ 3.0Ghz - 2x3870 @ stock = 11046
5000+ @ 3.0Ghz - 2x3870 @ 876/1254 = 11125

This makes no sense to me, I would estimate I picked up 600-800 points alone from oOCing my single 3870. Then when I OC 2 of them to the same spec's and I pick up less than 100 points :confused:I almost had 1 card running that fast.
 
The main problem is your cpu causing your score to be low. In fact, any AMD processor at the moment will severely bottleneck crossfire.

For a mild overclock, i just use CCC. Otherwise, AMD GPU Clock tool is decent.
 
ThatGuy16 said:
The main problem is your cpu causing your score to be low. In fact, any AMD processor at the moment will severely bottleneck crossfire.

For a mild overclock, i just use CCC. Otherwise, AMD GPU Clock tool is decent.
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Yeah I was just using CCC, used Rivatuner to turn up fanspeed. My question is what was your 3dmark06 scores before the OC and after?
 
GPU overclocks help 3Dmark score, but only slightly (maybe a couple hundred points). And with an AMD cpu, your going to be bottlenecking it bad.

With my E8400 at stock, i got 15k in 3dmark. With it overclocked to 4.0Ghz i get 18.1k. My best is at 4.6Ghz which give me 20k.
 
Ok thought about this a bit, maybe figured out another issue. My mobo is a the MSI K9A2 CF 790X. That has 2x PCI-E 2.0 slots, and the 1st card runs at 16x, but I'm pretty sure when crossfired it cuts both down to 8x.

I'm pretty sure 8x PCI-E 2.0 is enough for 3870's, the question is would this affect the benchmark that much, would a 16x/16x setup benchmark higher with the same processor and videocards?
 
ThatGuy16 said:
You wouldn't se a difference between x8/x8 and x16/x16, the CPU is just holding them back too much.
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Thats strange then. My friend is using a 6400+ (3.2Ghz) and I had my 5000+ running at 3.0Ghz. I had 2x HIS 3870 OC'd at 852/1190. And he had 2x Sapphire Toxic 3870's running at stock clocks (800/1???) and my 3dmark06 score was 1110x and his was 12700.

That is a massive score difference and the only real difference between the setups was I am using the MSI K9A2 CF 790X chipset and he is using the MSI K9A2 Platinum with 790FX chipset so both his cards would run in 16x compared to my 8x.

Granted he was using XP to run his test and mine was on Vista, but I don't know what kinda score variation that would cause.
 
1Kurgan1 said:
Thats strange then. My friend is using a 6400+ (3.2Ghz) and I had my 5000+ running at 3.0Ghz. I had 2x HIS 3870 OC'd at 852/1190. And he had 2x Sapphire Toxic 3870's running at stock clocks (800/1???) and my 3dmark06 score was 1110x and his was 12700.
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Thats not strange. He has 2 16X slots. His CPU has 200mhz on yours and double the L2 cache.
 
StrangleHold said:
Thats not strange. He has 2 16X slots. His CPU has 200mhz on yours and double the L2 cache.
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But if the 16x slots don't matter because the 3870's can't send enough info to make those the bottle neck. Then your saying 200mhz and 512kb more L2 = 1600 points? Even if you were to say that meant 500 points that would seem quiet shocking to me.

Also both my cards had 52mhz on the GPU over his and probabl some memory mhz too, but I'm not sure of what thats running on his.
 
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Well, what i meant was, x16/x16 will improve performance IF your CPU was not such a bottleneck. If you want a new motherboard, you'll just need to go over to the Intel side to get the performance those cards need and buy something like a E7200, E8200 or E8400 and a X38 motherboard. I know its not cheap, but dual video cards require high end hardware.

Your friends score is higher because he's using a X2 6400+, and at that his score is suffering.

For an example, with my setup as it is with a single 3870, i get 12100 points in 3Dmark.
 
1Kurgan1 said:
But if the 16x slots don't matter because the 3870's can't send enough info to make those the bottle neck. Then your saying 200mhz and 512kb more L2 = 1600 points? Even if you were to say that meant 500 points that would seem quiet shocking to me.

Also both my cards had 52mhz on the GPU over his and probabl some memory mhz too, but I'm not sure of what thats running on his.
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Having 2 X16 slot will make a difference if you using higher end cards regardless of what CPU you have. That with 200mhz and double the cache. Other than having somebody else shove Intel down your throat.
 
Well the actual plan is to move up from my current 790X chipset to the 790FX to get some more OC'ing features. I can't really cross 3.0Ghz on my 5000+ BE on this board without voltage adjustments, but on my friends Platinum with voltage adjustments we had it running at 3.4Ghz which should bring it up in performance quiet noticeably.

But then again thats just for now, I been looking at the 9850 Black Editions :D Which should be all the CPU I would need.

But my last question comes along the lines of slot speeds once again. As far as CF goes what would be better for running a 3 card setup? 16x/16x/4x or 16x/8x/8x? I would assume the 16x/16x/4x would be the best way to go because the speeds only go up linear and adding the info that these setups could push that setup would be the most capable, just that the last card wouldn't offer a massive gain where on the 16x/8x/8x it would offer a decent gain.
 
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If your running dual cards, any AMD cpu is going to bottlneck, even the quad cores. I know, i switched from a 3.3Ghz X2 5600+ to what i have now.

The only way your going to get the performance those cards are capable of is to go intel like i suggested in my last post. Its pointless to upgade to another AMD board and get no gain.
 
ThatGuy16 is there anywhere in his post where hes talking about changing to Intel or asked if he should. I think he gets your point but this isnt a AMD vs. Intel thread.

He wanted to know why his frame rates dropped after he swaped out a 3870 for another one, plus if it would make a difference in 8x-8x or 16X-16X slots. With higher end cards it will if hes running a AMD or Intel. This isnt a GET A INTEL, GET A INTEL, Jump up and down and stomp your feet. Get a grip!

And your trying to claim there will be no difference in a 9850 and a X2 5000 or going from 16X-16X from 8X-8X slots. Give me a break!! Its true Intel is faster clock for clock, but in frame rates after a certain point its gets to be mute, you cant even tell it unless you have bonic eyes. Bragging rights mean nothing!
 
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ThatGuy16 said:
If your running dual cards, any AMD cpu is going to bottlneck, even the quad cores. I know, i switched from a 3.3Ghz X2 5600+ to what i have now.

The only way your going to get the performance those cards are capable of is to go intel like i suggested in my last post. Its pointless to upgade to another AMD board and get no gain.
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Comparing a 5600+ to a 9850 is apples to Oranges, the 9850 like said has 1MB more L2 cache and has 4mb more L3 (which the 5600+ don't have at all).

Plus I have seen quiet a few scores of 9850's at stock clocks with 2x 3870's getting 16k scores, thats higher than what your E8400 got at stock if I am correct.

Either way ty for the tips, will help me in my purchases.
 
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