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9800 GTX+/GTS 250 SLI OC

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Mansmind

New Member
Joined
Jul 27, 2010
Location
Gainesville, GA
Before anyone asks, I didn't get either of these cards with the idea in mind of either overclocking them, or benchmarking with them. I bought the 9800 to put in a new system because it's a decent card for not a lot of $. I just happened to have a GTS 250 lying around at the office, so thought I would bring it home and play. :)

I guess you could say I've got the bug, I built my first system from scratch a month ago, and started playing with overclocking the system about 3 weeks ago, so I have a lot to learn still.

I've read several times that you should really have 2 of the same GPUs for SLI, although that seems to be dated news. Either way, I put them together in SLI configuration and they seem to work fine at stock speeds. It's not a huge boost in performance... 15% at worst and 25% at best in FPS.

The fun began when I started trying to overclock the cards. I'm using Precision Tune for the adjustments and Furmark for tuning (without links either between the GPUs or the core/shader clocks). The best SLI overclock I've got that's "stable" is:

9800 - 845/2025/1250 stock 738/1836/1100
250 GTS - 740/1750/1020 stock 675/1500/900

While it may be stable in just about everything, it gives me fits in 3DMark Vantage. I start seeing artifacts, primarily in the water...actually only in the water (1st test scene). To get rid of it I have to back off the core clock on the 9800 to around 830...that's the only change. Even then I still see them from time to time but it's not consistent.

While benchmarking, I had one heck of a time even getting some of them to run. 3DMark06 and AquaMark3 (still can't get this one) especially. Yes I've applied the patches and deleted dlls, etc. I did get 3dm06 resolved.

I'm not sure how, or even if.. running in SLI affects the overclocking ability of cards, but in this case it certainly does. Just for kicks I disabled SLI and ran on the 9800 GTX+ alone.

I was able to get the core clock up to 855 and remain stable (860 locked). I haven't pushed the shader yet, and I almost know I can take the memory up above 1250 easily enough...probably 1300 or so (I did this even in SLI mode).

Disabling SLI made a significant difference in benchmark rankings in comparison with like systems. I suppose that is expected since when using SLI it lists me as 2x 9800 GTX+ which I'm certainly not.

Excuse my wordiness, but I wanted to get the process I've gone through out there in the hope that one of you with far more experience than I have can answer some questions:

1. Seems to be a bad idea to mate these two cards if you're going to try to push them, correct? That being said, running at stock speeds does give you some improvement.

2. Suppose I get rid of the GTS 250 and buy a much better GTX 480? Would I be able to run that in SLI with the 9800 GTX+ or would I run into the same issues? If so, would I be better to just get another 9800 GTX+?

3. Anyone know of any OC'ing tricks I could try with the 2 cards I already have that may give me more stability?

4. I have a feeling if I could get a little more voltage to the 9800 I could take it up some more. According to GPUz it's running at 1.20v max. Any way of changing this short of flashing the BIOS?


Before I forget, here's my system info (I need to put this in my sig):

i7-930 @4.2 on air
12GB Corsair DDR3 1600
Asus P6TD Deluxe
Corsair HX 1000 PSU
6 WD Caviar Black 1TB HD's 2 in Raid 0, 4 in Raid 10
Coolermaster HAF 932 case

If you have any thoughts, comments, or advice I would appreciate hearing it.

Thanks
 
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