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Overclocking the Radeon HD 4870: One Way to Make a Great Card Better
George Ross, October 9, 2008



Introduction
With the release of the RV770 this summer AMD's acquisition of ATI finally has started paying off. The introduction of the 48XX series of GPU's was a huge success making AMD competitive in the graphics arena. In addition to that AMD's aggressive pricing structure has helped bring the price of video cards in general back down to a reasonable level. Now this is all well and good, but how well does the famed 4870 overclock? Let's find out.

Overclocking the HD 4870
As the saying goes with all overclocks do at your own risk. I also recommend a good solid aftermarket GPU cooler with good case ventilation for the best results. For the purposes of this overclock I used the VF-1000 LED from Zalman, and a customized heatsink for the voltage regulators.


I started off buy flashing the BIOS of my test 4870 with the clock settings of 800/1100MHz (core/memory). The BIOS along with all the tools necessary to do this can be found at techPowerUp. Use the ATI flash tool to flash the BIOS that you download from the VGA BIOS collection. When running the 800/1100 BIOS the Overdrive utility in the Catalyst Control Center will allow the card to be clocked up to 990/1200MHz.

After using the auto-tune feature of the Overdrive utility I got a maximum of 860/1190MHz. I started running benchmarks and the video driver would crash. So I backed off the memory speed back to 1100Mhz and started bumping the GPU speed back until I landed on 840MHz. This is the point were I was able to run games without the video driver crashing. I also ran an eight hour UT3 bot match to make sure the overclock was stable.

Test Hardware
Here are the details on the system that was used in this overclock.

Processor Intel Core 2 Quad Q6700 @ 3.2GHz
Motherboard FOXCONN P45A-S
Memory GeIL Evo One 4GB DDR2 1066 (PC2 8500) @ 480 MHz (DDR 960) 5-5-5-15 Dual Channel Mode
Hard Drive Seagate Barracuda ES.2 ST3250310NS 250GB 7200 RPM 32MB cache SATA 3.0Gb/s
Video Cards SAPPHIRE Radeon HD 4850 @ 675 MHz core 1150 MHz (2300DDR) memory
Catalyst 8.8
 POWERCOLOR Radeon HD 4870 @ 750 MHz core 900 MHz (1800DDR) memory
Catalyst 8.8
 POWERCOLOR Radeon HD 4870 @ 800 MHz core 1100 MHz (2200DDR) memory
Catalyst 8.8
 POWERCOLOR Radeon HD 4870 @ 840 MHz core 1100 MHz (2200DDR) memory
Catalyst 8.8
Optical Disk Drive Pioneer DVR-215DBK
Operating System Windows Vista Ultimate x64 SP1

Gaming Benchmarks

A 4% increase in frames derived form a 12% increase in clock speed. Of course this helped the Crysis numbers, but only at high and very high settings. Devil May Cry 4 showed the most benefit from the overclock. Overall I was pleased with the results.

Power Consumption

A 2% increase in power consumption at load not bad at all.

Conclusion
I can not stress enough about how important good cooling is when overclocking the HD 4870. Even the voltage regulators put off a fair amount of heat, and should not be without some means of cooling.

The bottom line is a 90Mhz overclock without even tweaking the voltages and an overall 4% increase in average frame rates for the HD 4870 that was tested. What is nice is this was not one of those factory overclocked cherry picked GPU's. This one was just a plain old vanilla HD 4870. Good times.


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