So how did we overclock? Well, with two programs. One was the well known Overdrive function in the ATI driver suite and the other was via a tool from ATI that gave us the ability to move the core and memory voltage up.
Starting with the Overdrive side of things, you might find yourself thinking that it's hardly the best program to overclock. This is a bit of a mixed bag; it's great for newbies who want to do a bit of overclocking, but don't have to be concerned about increasing the clocks too high. On the other hand, because the maximum clocks the software offers are quite comfortable, it means that people who really want to get down and dirty with overclocking don't get loads of head room.
Today Overdrive was a bit different; inside it gave us the ability to move our core to 1000MHz and the memory to 1500MHz or 6000MHz QDR. Since we're using beta drivers for the HD 5970, we're not 100% sure if it's going to be like this for everyone when official drivers come out. For the most part we don't really care and that's not to sound like a bastard; the simple fact is that if you want to get higher clocks, there are programs out there that will let you achieve it.
The fact that companies like Sapphire have included over voltage software in the bundle does give us a fair bit of faith that overclocking will be quite a significant feature for the HD 5970 and for that reason the official drivers will probably carry with it the same maximum overclock options.
The other piece of software we used was provided by ATI. The ATI OverVolt Tool is exactly what it sounds like. It gives us the ability to increase the voltage, in this case the core and memory.
Inside we have the ability to move the core from 1.05v to 1.1625v. There's also the ability to move the memory from 1.1v to 1.15v. While normally you'd find the ability to move the sliders in increments, in this case your options are one or the other. What that means is you can move the core voltage to 1.1625v from 1.05v and the memory from 1.1v to 1.5v, but you can't move the memory to 1.11v, 1.12v etc. The same goes for the core, no incremental increase and it's the stock voltage or the increased one being your only options.
What this meant for us was that we felt comfortable moving the sliders straight over; we have to figure that ATI wasn't going to give us the option to run a safe voltage and a non safe one, so we just went for it.
What this all resulted in was a significant overclock. While normally we would take a picture of the first GPU-Z screen, it seems that it doesn't want to recognize our increase in core and memory clock. Instead we've used the next tab which gives us the ability to see what the cores are running at. Telling it that we want to see the maximum speed the core and memory run at, we can clearly see the clocks that we achieved.
What we were able to achieve was a core of 890MHz and a memory clock of 4775MHz QDR. Now, if you think about what we started with, 725MHz on the core and 4040MHz QDR on the memory, you quickly begin to realize the massive OC we have on our hands. With the clock achieved and the ability to run the 3DMark Vantage test multiple times without skipping a beat, it was time to get into the rest of our benchmarks to see what kind of performance increase these clocks offered.
Before we jump to the next page, we just want to mention these weren't the first clocks we tried. I spent a good few hours trying to find the sweet spot and at some states it looked like 900MHz + was going to be an option, but it didn't seem to want to happen with the memory this high. While we might have been able to drop the memory and achieve a higher clock, we found ourselves pretty happy with the position above. The clocks we achieved ran all our benchmarks stable and gave us a significant increase over the stock ones.