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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 X1950XTX
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Diamond HD 4850
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Palit HD 3870
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AC
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DC (Est.)
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AC
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DC (Est.)
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AC
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DC (Est.)
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Idle
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+49W
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+42W
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+59W
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+50W
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+20W
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+17W
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Load
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+131W
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110W
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+120W
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101W
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+84W
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72W
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The HD 3850/3870 showed us that high performance graphics card could also be
frugal when it came to power consumption. The HD 4850 is a complete reversal,
bringing us back to the days of the X1900 and HD2900 series. Idle power consumption
was horrendous at 50W, higher than any card we've tested.
The load power
was a far more acceptable 101W, which is not bad considering the HD 4850's performance.
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Installed.
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The high idle power consumption made us wonder whether the card was throttling
properly in 2D mode, but GPU-Z confirmed the core and memory speeds were decreased
when idle. It was a very minor underclock, however, and judging by the power consumption
figures, it seems that ATI PowerPlay — tasked with throttling
the clocks and voltage to save power when the GPU is not being stressed — is
either not working or not fully implemented at this time. It's possible that
the PowerPlay settings for the HD 4000 series are controlled on the driver-level
instead of BIOS-level,
as was the case of the HD 3000 series. As mentioned earlier, there were no offical Catalyst drivers for the card at time of testing.
There is an ongoing discussion about the matter in our
forums, with some users reporting success using modified BIOSs to change
how the card throttles down. As a disclaimer, we should note that altering your
video card's BIOS can be dangerous. Proceed with caution if you dare.
VIDEO PLAYBACK
The HD 4000 series utilizes UVD 2, an updated version of ATI's Unified Video
Decoder to offload video decoding to the GPU. The HD 4850 handled all our playback
clips with ease. Despite high incidences of CPU usage during the Drag Race clip,
it played smooth without any skips or anamolies in either the video or audio.
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Video Playback Results
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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 (H.264)
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3%
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8%
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~136W
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Coral Reef (WMV3)
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28%
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39%
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~151W
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Flight Sim. (WVC1)
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55%
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76%
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~168W
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Drag Race (WVC1)
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73%
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88%
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~176W
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UVD 2 though does not seem to provide a significant improvement in offloading
though, posting virtually identical CPU utilization numbers as the HD 3870 and
UVD 1. The HD 4850's high power consumption is also evident during HD playback,
pulling between 20-40W more from the wall than the HD 3870 or nVidia's Geforce
9600GT. As a pure playback device, it's not very efficient, at least with the
current set of beta drivers.
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Video Playback Comparison
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Video Clip
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Diamond HD 4850
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Palit HD 3870
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Asus EN9600GT
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Mean CPU
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Peak CPU
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Mean CPU
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Mean CPU
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Peak CPU
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AC Power
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Mean CPU
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Peak CPU
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AC Power
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Rush Hour (H.264)
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3%
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8%
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~136W
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3%
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9%
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~105W
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2%
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7%
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~113W
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Coral Reef (WMV3)
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28%
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39%
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~151W
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27%
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41%
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~118W
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15%
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30%
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~121W
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Flight Sim. (WVC1)
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55%
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76%
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~168W
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50%
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78%
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~130W
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28%
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46%
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~131W
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HDMI OUTPUT
The HD 4850 is the first ATI card that we've been able to get working properly with HDMI audio
in our test setup. We weren't able to test its full 7.1 functionality
with our BenQ FP94VW monitor as it outputs sound via a stereo headphone jack.
The graphics driver wasn't able to detect/deliver
our monitor's native resolution of 1440x900. 1280x768 was the closest it would
allow, and thus the resulting image was slightly degraded due to scaling. The
available resolutions were more ideal for a HDTV rather than a LCD monitor equipped
with HDMI, which is probably appropriate.
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Available resolutions via HDMI.
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