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Radeon HD 4850 Vs. GeForce GTS 250: Non-Reference Battle

Overclocking The Asus EAH 4850 Matrix Using iTracker

When overclocking a garden-variety Radeon HD 4850, the ATI Overdrive utility will cap out at 700 MHz GPU speed. Fortunately, the BIOS on the Asus 4850 Matrix ups this to 800 MHz, allowing us to push our GPU past the stock 750 MHz speed of a Radeon HD 4870. And push it we did.

The ability to adjust the voltages on the GPU and memory will really break the chains usually imposed on most overclocking attempts. Increasing the voltage is a fundamental overclocking technique, and we probably wouldn’t have gotten past 700 MHz on the GPU core without it.

After doing a little research, we found that a stock Radeon 4870 has a GPU voltage somewhere in the neighborhood of 1.263 V. We thought this would be a good place to start for the GPU, but it wasn’t quite enough as we took it to 1.33 V for our maximum stable overclock.

After many attempts and settings, we cranked the Asus EAH4850 MT from a stock speed of 625 MHz GPU/1,986 MHz memory to 764 MHz GPU and 2,013 MHz memory. This GPU overclock is very good for a Radeon HD 4850--an increase of 139 MHz over stock and surpasses even the Radeon HD 4870 stock clock speed by 14 MHz. Unfortunately, the memory wasn’t nearly as accommodating, with a slight overclock of 19 MHz DDR at 2.03 V.

We actually got much higher GPU clocks out of the card, but after repeated testing, it was clear we had to back off a bit to reduce temperatures and prevent visual artifacts. But the final 764 MHz GPU and 2,013 MHz memory clocks were rock solid throughout all of our benchmarks and stress tests.

One of the great things about the iTracker utility is not only its overclocking capabilities, but its underclocking features as well. The utility allows us to set an extremely low clock speed and voltage for 2D use in Windows, and a high clock speed and voltage for 3D use in the same profile.

However, we did come across one slight complication when underclocking: after we had some crashing problems launching Fallout 3, we did a ton of testing to diagnose the issue. It turns out, if the 2D clock is set too low--say at 300 MHz--some applications will falter when ramping up to 3D clock speeds. Both Fallout 3 and Far Cry 2 demonstrated this behavior. Once we boosted the speed to 400 MHz, the problem no longer occurred. 

After all is said and done, we can’t say enough about the ability to modify voltages in the iTracker utility for the sake of both overclocking and underclocking. It’s a great tool with which to work, and after we got over some of the poor interface design decisions, we truly wish everybody made a tool like this for their products.