PowerColor SCS HD4650: A Fanless Budget Graphics Card

Graphics Cards
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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. 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)
Card
Est. Power (Idle)
Est. Power (Load)
PowerColor SCS3
HD 4650
15W
28W
Asus EAH3650
18W
39W
ATI Radeon HD 4670
3W
40W

Our PowerColor HD 4650 exhibited slightly lower power consumption than Asus' passively-cooled HD 3650 when idle (3W), and significant savings at full load (11W). It's a nice improvement considering the 4650 is the 3650's direct successor. The HD 4670 remains the king of idle power consumption however, even though it is faster and uses much of the same software and hardware under the hood.

It's difficult to pinpoint exactly why the idle power is so high. It may be the result of differences in chipset implementation by the manufacturer, or the use of slower, yet more power hungry memory, or a combination of both. It's hard to believe either factor alone could result in an extra 12W. We doubt drivers are the issue — ATI has had plenty of time of to sort out any serious power issues for their HD 4000 series, especially since they release a new set of drivers every month. Some form of power management was in effect — the core/memory speeds lowered to 300/299MHz when the system was idle and during video playback it alternated between idle and reference speeds.

Video Playback

Video Playback Comparison
Video Clip
HD 4650
HD 3650
HD 4670
Mean
CPU
AC
Power
Mean
CPU
AC
Power
Mean CPU
AC
Power
Rush Hour
(H.264)
4%
~102W
2%
~102W
3%
~94W
Coral Reef
(WMV-HD)
30%
~115W
28%
~117W
28%
~105W
Drag Race
(VC-1)
64%
~137W
72%
~141W
63%
~129W

As the video decoding hardware is the same in both the HD 3000 and 4000 series, CPU usage measurements were unsurprisingly similar, passing every test with ease. The HD 4650's power consumption during video playback was within a few watts of its predecessor, the HD 3650, but far behind the ultra-efficient HD 4670. This is due to the higher idle power consumption of the HD 3650 which carries over to light-load situations like video playback.



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