Asus Radeon HD 4870 Matrix

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The power consumption of an add-on video card can be estimated by comparing the total system power draw with and without the card installed. Our results were derived thus:

1. Power consumption of the graphics card at idle - When CPUBurn is run on a system, the video card is not stressed at all, and stays in idle mode. This is true whether the video card is integrated or an add-on PCIe 16X device. Hence, when the power consumption of the base system under CPUBurn is subtracted from the power consumption of the same test with the graphics card installed, we obtain the increase in idle power of the add-on card over the integrated graphics chip (Intel GMA950). (The actual idle power of the add-on card cannot be derived, because the integrated graphics does draw some power — we'd guess no more than a watt or two.)

2. Power consumption of the graphics card under load - The power draw of the system is measured with the add-on video card, with CPUBurn and FurMark running simultaneously. Then the power of the baseline system (with integrated graphics) running just CPUBurn is subtracted. The difference is the load power of the add-on card. (If you want to nitpick, the 1~2W power of the integrated graphics at idle should be added to this number.) Any load on the CPU from FurMark should not skew the results, since the CPU was running at full load in both systems.

Both results are scaled by the efficiency of the power supply (tested here) to obtain a final estimate of the DC power consumption.

Power Consumption Comparison (DC)
Est. Power (Idle)
Est. Power (ATITool)
Est. Power (FurMark)
ATI HD 4830*
Diamond HD 4850
Asus ENGTX260
ATI HD 4870 1GB
Asus HD 4870 512MB Matrix**
* sample with unknown number of stream processors
** average idle power used

Even though ATI's card had an extra 512MB to power, the overclocked Asus Matrix drew an extra 6-7W DC on a full load. On the bright side, idle power was actually lower by almost 20W — the Power Saving mode during 2D use pays off.


The Matrix card had a nifty utility to display the card's operating voltages and frequencies. The ATI card had no such application, so to get a better idea of its inner workings we took a look at the board's BIOS. We used GPU-Z to extract the card's BIOS and Radeon BIOS Editor to examine how the card's clock speeds and voltages were set to behave.

ATI HD 4870 1GB: BIOS Clock/voltage settings.

Displayed in green, yellow and red are the card's settings for idle, UVD, and 3D. We confirmed the frequency changes with GPU-Z, but the BIOS shows us a voltage jump of 0.060V when the 4870 1GB enters 3D mode.

ATI HD 4870 1GB: BIOS Fan settings.

The fan control behavior follows a simple linear progression starting at a GPU temperature of 58°C and finishing at 101°C.

Asus HD 4870 512MB Matrix: BIOS Clock/voltage settings.

The Matrix's BIOS shows the voltages locked at 1.263V — you're expected to use iTracker if you want any power savings. The fan control panel was greyed out, so we still have no insight into the how the card's main fan operates.

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