Is anyone into overclocking?

[DeeBye]

Jarulf's several posts about his new mighty 7900GTX had me thinking about my own 7600GS. It's certainly not in the same league as a 7900GTX, but it's a great card for the price. I paid about $85 CDN after rebate (which was an incredibly awesome deal and should have deserved a "DeeBye's Freebies" thread", and it performs somewhere between a 6600GT and a 7600GT. I can play Oblivion on "high" settings @ 1024x768 @ 45 fps.

Well, one thing I remember about the research I did before I bought it is that the 7600GS is apparently a great overclocker. It's essentially an underclocked 7600GT with a passive heatsink instead of a fan. None of the pipelines are disabled in any way. They just underclocked it, exchanged the fan for a passive heatsink, and used a more energy-efficient design.

I don't have a whole lot of experience overclocking videocards, but what I do know is that temperature governs the limit to which one can overclock. I've recently been keeping tabs on my GPU temperatures, and I can already tell that my 7600GS is a great candidate for overclocking. It idles at 39°C, and after an hour of the 3DMARK05 demo (my son liked watching it okay?), it only crept up to 43°C. 30 seconds at idle and it is back down to 39°C again.

I've already enabled CoolBits in my nVidia Control Panel, so I have access to the clock frequency settings. My 7600GS is factory clocked at 420 MHz core / 400 MHz memory. I'm not looking for incredible bleeding-edge performance. I'm looking for a slight but noticeable performance increase, without even coming close to risking damage. What settings would you recommend, and is there any specific program that I should use to stress test my card after adjusting my clock settings?

[Roland]

First:
Get a fan. Buy an aftermarket cooler (Zalman makes some great products), and stick it on there. Preferably something that comes with RAM heatsink chips, as well, especially if your card does not already have the RAM cooled seperately from the main heatsink. Or, if it doesn't come with the main cooler, buy some seperately. They're dirt cheap (~$10), and will help take some of the heat off. It won't be allow for a HUGE increase, but anything is better than nothing, and it could be the difference between overclocking a small bit, and not at all.

Second:
Check out Tom's Hardware Guide. Look for any reviews on the 7600GS. Also check AnandTech. They do many hardware reviews as well. This will give you a rough idea of just how far the limit is, so that you know a relative ceiling without having to find it out on your own.

Third:
Small increments. I cannot stress this enough: SMALL INCREMENTS! 1 MHz - 2 MHz are a good start, but NEVER go beyond 5 MHz at a single time. After each and every increase in clock speeds, check your temperatures at idle, and then play Oblivion. Push that card hard, and look for any tell-tale signs of distress, namely artifacting. You'll know it when you see it (remember pushing on the LCD screen of a calculator as a kid to make all the pretty colors show up? Imagine that, in bits and pieces, all over your screen at random intervals. That's artifacting). You'll probably be able to push the Core clock further than the Memory clock, so bear that in mind. They do not have to be raised equally. You could raise the Core clock by 50 MHz, and the Memory clock only 30 MHz. You can raise both at the same time, but just be aware that one will certainly go farther than the other. One other thing to note is that sometimes decreasing the Memory clock by a few MHz will allow you to safely increase the Core clock by a few more MHz, and gain you a bit more performance. This applies vice versa, as I recall from my own testing, but more often than not it's the former case.

So, to summarize:
1) Active VGA cooler. Trusted company.
2) Check reviews to find a relative safe overclocking ceiling.
3) Baby steps!

Good luck, and if you have any further questions or problems, feel free to ask.

[DeeBye]

Second:
Check out Tom's Hardware Guide. Look for any reviews on the 7600GS. Also check AnandTech. They do many hardware reviews as well. This will give you a rough idea of just how far the limit is, so that you know a relative ceiling without having to find it out on your own.

I found this review, which included overclocking results. They were easily able to get a 20% overclock on the stock heatsink, which is what I am going after. I don't want a fan because one of the things I really like about my 7600GS is that it is silent. Besides, even with the 20% overclock, the reviewed card idled at 42°C and only hit 60°C at load. Those kinds of temps shouldn't require a fan, right? Mine isn't a MSI card, but it should perform much the same.

I suspect that with a 3rd party VGA cooler one could overclock a 7600GS right up to 7600GT levels.

[DeeBye]

Here are the results of my initial overclocking attempts. I used the Free Edition of 3DMARK05 to benchmark the changes. I know it's not a completely accurate representation of 3D performance, but it's a good enough way to check performance between changes in clock settings.

Stock settings
420 MHz core / 400 MHz memory
40°C idle temp
3948 3DMARK05 score
40°C after benchmark

Attempt 1
431 MHz core / 410 MHz memory (+2.6% / +2.5%)
40°C idle temp
4071 3DMARK05 score (+3.1%)
40°C after benchmark

Attempt 2
441 MHz core / 420 MHz memory (+5.0% / +5.0%)
40°C idle temp
4138 3DMARK05 score (+4.8%)
40°C after benchmark

Attempt 3
451 MHz core / 451 MHz memory (+7.4% / +12.8%)
40° idle temp
4344 3DMARK score (+10.0%)
40° after benchmark

I left off there. I haven't really done any stress testing at the 451/451 overclock, but I don't foresee any trouble hitting 500/500 overclock on the stock heatsink. For reference, the 7600GT is clocked at 560/700.

[SwissMercenary]

The only two cents that I can add, is that if you *really* want to stress your card, play Guild Wars, or just leave it running, Anti-aliasing 4x.

For me, GW runs some 10 degrees hotter then... Well, any other game. It routinely causes my card to overheat in the summer, too, even with a desk fan blowing straight into the open case.

[kandrathe]

Increasing speed due to cooling is proportional to the amount you reduce the temperature compared with absolute zero. For example, your machine is running at about 312K-316K. So for each 5% improvement in processing speed you need to reduce the temperature by 16C degrees. You probably have some additional cooling capacity in your heat sink/fan -- after that additional overclocking requires something beyond air.

Overclocking Video how to guide.