Redefining Budget Gaming Graphics: ATI's HD 4670

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POWER

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 on our test system. 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 system power under CPUBurn with just the integrated graphics is subtracted from the system power under CPUBurn with the add-on card, we obtain the increase in idle power of the add-on card. (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 ATITool 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 ATITool should not skew the results, since the CPU was running at full load in both systems

Power Consumption Comparison
GPU State
ATI HD 4670
Asus EAH3650
ATI HD 3850
AC
DC (Est.)
AC
DC (Est.)
AC
DC (Est.)
Idle
+4W
+3W
+21W
+18W
+13W
+11W
Load (ATITool)
+44W
38W
+43W
37W
+64W
55W
Load (FurMark)
+47W
40W
N/A
N/A

By our measurements the HD 4670 used a surprisingly low amount of power at idle — only 3W. We've never encountered a card with such a low power draw before. During load with ATITool, the card used about 38W, more or less matching the Asus HD 3650, the last Radeon we reviewed. Using FurMark, the power draw was additional 2W. The HD 3650 did not match the low idle power of the previous generation HD 3850, but the HD 4670 has clearly leapfrogged ahead in this regard..

PowerPlay, ATI's power management technology seemed to be very attentive with the HD 4670. According to GPU-Z, when idle the clocks stayed at 165/250Mhz. During video playback the core clock varied between 165Mhz and 300Mhz, and the memory speed varied between 250Mhz and 500Mhz. At full load, clock speeds rose up to the maximum 750/999Mhz.

Video Playback

The HD 4670 handled our video playback testbed with ease. CPU usage during playback failry low except for our more demanding VC-1 clips. The H.264 Rush Hour 3 trailer had a trivial effect on system resources.

Video Playback Results: HD 4670
Video Clip
Mean CPU Usage
Peak CPU Usage
AC Power
Rush Hour
3%
8%
94W
Coral Reef
28%
40%
105W
Flight Sim.
56%
70%
120W
Drag Race
63%
77%
129W

In terms of CPU usage, video playback was very similar to the previous Radeons. The HD 4670 ,however, used less power during video playback than both the HD 3650 and 3850.

Video Playback Comparison
Video Clip
HD 4670
HD 3850
EAH3650
Mean
CPU
AC
Power
Mean
CPU
AC
Power
Mean
CPU
AC
Power
Rush Hour
3%
94W
3%
~98W
2%
~102W
Coral Reef
28%
105W
28%
~109W
28%
~117W
Flight Sim.
56%
120W
55%
~125W
60%
~133W
Drag Race
63%
129W
N/A
N/A
72%
~141W


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