Widescreen Gaming Forum

Last week I got a 7950 OC from Sapphire. It will replace my two 6950’s, I was only using one of them, because of severe microstutter problems. I just wanted to share my overclocking results, so here we go:

First of all I found this page. It is a roundup of all reviews in which overclocking was done. Keep in mind that reviewers normally receive handpicked cards, which will probably overclock further than the average card we buy. Besides that they mostly use benchmarks like 3dmark11 to see how high a card can go. That is not really useful for us since we game a lot and overclocks might be stable in benchmarks, but not in games.

The level of voltage were the average reviewer hit a wall was between 1200mv and 1250mv. I downloaded the latest version of Afterburner (2.2.0 beta12) and set the voltage to 1200mv. I am using the second bios. This one has been altered by sapphire with slightly higher voltage and powerplay limits I believe, but don’t quote me on that one. The next step was to see how high a core clock I could reach without seeing artifacts or without the card freezing up. At a core clock of 1200mzh I saw artifacts in the second test of 3dmark11 at 1190mzh they were gone (yes I know, not the best way to test an oc, but a good indication). When playing BF3 the artifacts were visible until I reduced the core speed to 1150mhz. The only way you will ever know if the oc is stable is by playing games a lot (I know, hard work ;)). It is important to note that when you try to find the minimum voltage needed to run a curtain clockspeed the artifacts come back. So artifacts aren’t linked to clockspeed only, but to voltage settings as well. The max speed for the memory in Afterburner is 1600 and my card seems stable at that speed. Unofficial overclocking isn’t working, because of a powerplay bug. It is very likely that a new driver 12.3 or 12.4 will have that fixed.

At 1150/1600 the 3dmark11 performance score went from 7250 to 8700. These 79xx clock like crazy. Keep in mind that every card is different so you might be getting higher or lower results depending on luck. Even with this oc the card stays cool at 64 Celsius after playing a couple of hours of BF3. Besides that I can’t even here the fan. I read a lot of positive reviews and the authors weren’t excaturating.

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Philips BDM4065UC(3840x2160) Acer Z35(2560x1080@200hz); 980 Ti Hybrid @stock ; 6700K 4.6ghz (1.35v)/D15; 16GB 3200mhz; Asus Maximus Ranger VIII; AX860; 1TB 960 EVO; 750GB 840 EVO; Teufel Concept D 500; Sennheiser HD6XX; Windows 10 (latest build)

:twothumb

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- AMD 965 @3.8 - Gigabyte 790fx ud5 - AMD 7970 Ghz - OCZ Reaper 4GB - OCZ Vetex - Eyefinity 3x Asus vw266h - Samsung t260hd + 226ux - (soundcard) - Sony 5.1 ~700w - PC P&C 750w - Corsair K60 -

After fine-tuning the overclock the past two weeks I have found a couple of things. Even though Battlefield 3 is a resource heavy game, some games that are not can show that you overclock is not stable and/or artifact free. I had to lower my overclock on the core from 1150 to 1130 to eliminate artifacts that showed up in different games. When that was done I tried to find the minimal voltage that was needed for that speed. I was still using 1200mv and lowered that until games crashed. This was at 1140mv. The funny thing was that it seemed very stable on 1150mv, but games stuttered sometime. At first I thought it was a driver problem but that didn't seem to be the case (tip: never change drivers when you are fine-tuning your overclock otherwise you don't know what causes the problems you might have). So even though you don't get artifacts or games crash on you, it doesn't mean that your overclock is stable. The stuttering wend away when I increased the voltage to 1160mv. There must be some throttling going on or something.

Fine-tuning the voltage like this isn't even necessary and may seem a bit obsessive ;) (and you would probably be right), but I always like to keep my hardware as cool as possible (without too much noise from fans) so it doesn't break before I replace it. Remember overclocking doesn't reduce the lifespan of hardware, but exposure to heat does.

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Philips BDM4065UC(3840x2160) Acer Z35(2560x1080@200hz); 980 Ti Hybrid @stock ; 6700K 4.6ghz (1.35v)/D15; 16GB 3200mhz; Asus Maximus Ranger VIII; AX860; 1TB 960 EVO; 750GB 840 EVO; Teufel Concept D 500; Sennheiser HD6XX; Windows 10 (latest build)

Your observations about different games loading differently are spot on - for a while I was helping out a friend in a Folding competition (or rather, I was helping his team) and I could get GTX460s folding stably at 925MHz @ 1.025 Vcore... I couldn't get games stable on that Vcore any higher than 815MHz. Or rather, I couldn't get Surround games running any faster than that. Single screen was good to about 875Mhz.

Thanks for the info, though; I'm holding out to replace my nVidia Surround with a 7970, although due to other issues, I probably won't get around to it until after the launch of Kepler, which means I may stick with nVidia. Will wait and see. ;)

Today I had some spare time and overclocked the vram of my 7950 some more. Afterburner lets you increase the voltage from 1.6 (stock) to 1.7, which I did. 1800mhz seems stable, but need to play more games to verify this. Can bench at 1950mhz, but in games that clockspeed isn't stable. Traditionally overclocking the gpu yields a higher performance increase than overclocking the vram. I noticed that this might not be true at triplewide resolutions. With 3dmark11 you see a small increase in scores when overclocking the vram, but in games the fps gain is rather large. So when overclocking give your vram a little more attention than you normally would if you play you games at higher resolutions.

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Philips BDM4065UC(3840x2160) Acer Z35(2560x1080@200hz); 980 Ti Hybrid @stock ; 6700K 4.6ghz (1.35v)/D15; 16GB 3200mhz; Asus Maximus Ranger VIII; AX860; 1TB 960 EVO; 750GB 840 EVO; Teufel Concept D 500; Sennheiser HD6XX; Windows 10 (latest build)

Even on 1920*1080 you see a performance increase! At least in Crossfire in Crysis!



So overvolting your VRAM did help increase the max limit ? Didn't realy help with my two 7970. older version of Afterburner had a limit off 1790mhz :( to bad ^^ but now its around 2200 or such... Well, my HD7970 has Vram limit around 1975 or such.... no matter what Voltage. Sadly not getting over 9000 ;( truly hurts me!

But strange thing is, Playing Firefall i could OC Vram & GPU higher than with Furmark or other Benchmark tools!

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We gonna send it to outa space!

Even on 1920*1080 you see a performance increase! At least in Crossfire in Crysis!

Yes indeed, but my point was that the increase is relatively higher at higher resolutions.

So overvolting your VRAM did help increase the max limit?

While benching increasing the voltage helped a little, but when playing games it made the higher overclocks more stable.

But strange thing is, Playing Firefall i could OC Vram & GPU higher than with Furmark or other Benchmark tools!

Weird, normally it is almost always the other way around. Not sure how intensive Firefall is though.

My plan is to search for the maximum stable vram clockspeed while gaming the next couple of weeks. When I am sure the overclock is stable I will turn down the voltage untill it becomes unstable again.

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Philips BDM4065UC(3840x2160) Acer Z35(2560x1080@200hz); 980 Ti Hybrid @stock ; 6700K 4.6ghz (1.35v)/D15; 16GB 3200mhz; Asus Maximus Ranger VIII; AX860; 1TB 960 EVO; 750GB 840 EVO; Teufel Concept D 500; Sennheiser HD6XX; Windows 10 (latest build)

The last couple of months I had problems with intermittent stuttering. It turned out to be a bad oc on my gpu. The problem is that although an oc seems very stable (no blue screens, no freezes etc.) it can still be ‘unstable’. After adding an additional 20mv I have seen no stuttering what so ever. Although oc guides tell you to up the voltage until you have no more blue screens for example, it might be prudent to add a little more voltage as a buffer so no stuttering will appear.

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Philips BDM4065UC(3840x2160) Acer Z35(2560x1080@200hz); 980 Ti Hybrid @stock ; 6700K 4.6ghz (1.35v)/D15; 16GB 3200mhz; Asus Maximus Ranger VIII; AX860; 1TB 960 EVO; 750GB 840 EVO; Teufel Concept D 500; Sennheiser HD6XX; Windows 10 (latest build)