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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
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Power Consumption Comparison
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GPU State
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ATI HD 4670
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Asus EAH3650
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ATI HD 3850
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|
AC
|
DC (Est.)
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AC
|
DC (Est.)
|
AC
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DC (Est.)
|
|
Idle
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+4W
|
+3W
|
+21W
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+18W
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+13W
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+11W
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Load (ATITool)
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+44W
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38W
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+43W
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37W
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+64W
|
55W
|
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Load (FurMark)
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+47W
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40W
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N/A
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N/A
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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.
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Video Playback Results: HD 4670
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Video Clip
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Mean CPU Usage
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Peak CPU Usage
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AC Power
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|
Rush Hour
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3%
|
8%
|
94W
|
|
Coral Reef
|
28%
|
40%
|
105W
|
|
Flight Sim.
|
56%
|
70%
|
120W
|
|
Drag Race
|
63%
|
77%
|
129W
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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.
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Video Playback Comparison
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|
Video Clip
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HD 4670
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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
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28%
|
~117W
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|
Flight Sim.
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56%
|
120W
|
55%
|
~125W
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60%
|
~133W
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|
Drag Race
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63%
|
129W
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N/A
|
N/A
|
72%
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~141W
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