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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.
|
Estimated Power Consumption Comparison (DC)
|
|
Card
|
Idle
|
Load
|
|
ATI Radeon HD 5450 512MB
|
6W
|
7W
|
|
Asus EN9400GT Silent 512MB
|
11W
|
23W
|
|
PowerColor HD 4650 512MB
|
15W
|
28W
|
|
ATI HD 4770 512MB
|
28W
|
60W
|
|
Asus EAH5750 Formula 1GB
|
25W
|
77W
|
|
Asus EN9800GT Matrix 512MB
|
32W
|
80W
|
|
ATI HD 4830 512MB
|
18W
|
87W
|
|
Sparkle GeForce GTS 250 1GB
|
22W
|
87W
|
|
PowerColor HD 5850 1GB
|
21W
|
132W
|
The HD 5450 is easily the most energy efficient graphics card we've tested,
using half the power of the GeForce
9400 GT when idle, and less then a third on load. Throwing this card
on a motherboard equipped with its own integrated graphics won't draw much extra
power.
The Asus EAH5750 Formula falls between the HD
4770 and 4830, using
25W idle and 77W on load, a reasonable amount for a midrange card.
Video Playback
|
Test Results: Video Playback
|
|
Test State
|
ATI Radeon HD 5450
|
Asus EAH5750 Formula
|
|
Avg.
CPU Usage
|
Avg. DC Power*
|
Avg.
CPU Usage
|
Avg. DC Power*
|
|
Rush Hour
(1080p H.264)
|
4%
|
+13W
|
6%
|
+7W
|
|
Coral Reef
(WMV-HD)
|
27%
|
+24W
|
28%
|
+55W
|
|
Spaceship
(1080p x264)
|
3%
|
+6W
|
3%
|
+27W
|
|
*compared to idle
|
Both the 5450 and 5750 passed our video test suite with ease, though the HD
5450 used considerably less power doing so. This was particularly notable during
WMV-HD playback as we noticed that the 5750's clock speed was set to maximum
rather than the UVD-prescribed 400/900MHz. It's a problem we encountered on
the HD 5850 as well. The 5450, which uses almost as much power on load as when
idle, was not as affected.
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