Overclocking Results:

stock overclocked gpu (core) speed: 750 mhz 800 mhz memory speed: 1800 mhz 2200 mhz ddr2 if you're new to Overclocking and not sure what to do, check out these two excellent Guides for some pointers: Overclocking the CPU and Memory Overclocking the Videocard

The Palit HD 4870 X2 videocard uses ATI's stock memory and GPU timings of 900Mhz (1800Mhz DDR) and 750Mhz respectively, so PCSTATS was hoping to get some good overclocking results out of it. Were we successful? Read on...

As usual, we will start by increasing the GPU speed in 25Mhz increments, followed by the memory in 50Mhz blocks We take note of any stability problems or the appearance of artifacts, and then list the maximum stable and artifact-free overclocked speed the video card can attain.

The Palit HD 4870 X2's twin R770 GPUs successfully achieved 775Mhz and 800Mhz without any sign of artifacts or instability. Sadly, we were not able to achieve a stable overclock beyond this point. Possibly the complicated nature of the internal connection between the card's two GPUs is limiting the overclocking potential here?

The memory was next, and proved a bit more successful. We easily cruised past the 950Mhz and 1GHz marks, and also managed to run the card stably at 1050MHz and 1.1GHz, before the appearance of video artifacts curtailed our fun. The Palit HD 4870 X2 topped out at a respectable 1.1GHz (2.2GHz DDR) memory speed, proving that whatever is limiting the GPU's overclocking potential does not bother the memory side of things.

The Palit HD 4870 X2 is not going to set the world on fire with its overclocking ability just yet, but that's not really the advertised purpose of the card. The Radeon HD 4870 X2 chipset is designed to provide a high-end single card gaming experience out of the box, and next up we will see if that's what it truly does.

Tweaking Fan Speed for Lower Temperatures

After a few rounds of benchmarking with the Palit HD4870X2, it quite literally became too hot to touch. Curiously, in spite of the burn-your-fingers-heatsink-temperature, the videocard's 60mm fan remained relatively slow and quiet throughout testing, even while running an intensive set of Crysis benchmarks at 1920x1200!! It's a safe bet the videocard's twin GPUs were generating heat like fiery furnace, and sure enough GPU temperatures were hovering around the 80-90C mark. The memory heatsink along the top of the card was an astounding 60C.... far from ideal conditions regardless of how quiet the videocard was operating.

Why the heatsink's fan wasn't kicking up the RPM to deal with the heat is a question only AMD can address, drivers always seems to its weakest point. Luckily, there is a quick software hack you can do to dramatically lower GPU and memory temperatures. Credit is due to Guru3d for coming up with this one, and you'll find that it applies to just about any ATI Radeon videocard on the market now.

First ensure that Catalyst 8.8 drivers are installed (or newer), then open up Catalyst Control Center and go to > ATI Overdrive > and enable overdrive by clicking on the little padlock icon. Next, click on Profiles > Profile Manager and create a new profile called "Lower Fan Tweak". Check "all catalyst control center settings" and click Save. Next, within Windows Vista go to:

C:\Users\*your ID*\Appdata\Local\ATI\ACE\Profiles\Lower Fan Tweak.xml

Right click on the file and select "edit", we need to edit some parameters in the XML.

Find "FanSpeedAlgorithm" and change value="Automatic" to value="Manual". The term "manual" is case sensitive, so spell it Manual.
Next, find "FanSpeedPercentTarget_1" and change to your desired fan speed percentage, value="100" for full fan speed, value="50" for half, you get the idea. The number may be 23, or some other integer.

Note that if you change the values for FanSpeedPercentTarget_0, this won't work on the dual GPU HD 4870 X2 videocard - that parameter (the "_0" parameter) is for the single GPU Radeon HD 4870 videocards. I made this mistake the first time and it took me a couple minutes to figure out why the fan speed didn't change at all.

Save the XML file you've just edited. Back in the Catalyst Control Center load up the "Lower Fan Tweak" profile. You should immediately notice the fan on the Palit HD 4870 X2 speed up to 100% duty.

For our testing PCSTATS simply set the value to 100, which results in a pretty vigorous whooshing noise. Within a few minutes the GPU temperature fell from 82C to 46C, and fan speed had risen from 1300RPM (23%) to 4700RPM (100%). If you play around with the values you'll find a happy medium to achieve low temps and moderate noise levels.