Diamond Radeon HD4850

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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 X1950XTX
Diamond HD 4850
Palit HD 3870
AC
DC (Est.)
AC
DC (Est.)
AC
DC (Est.)
Idle
+49W
+42W
+59W
+50W
+20W
+17W
Load
+131W
110W
+120W
101W
+84W
72W

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.


Installed.

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.

Video Playback Results
Video Clip
Mean CPU Usage
Peak CPU Usage
AC Power
Rush Hour (H.264)
3%
8%
~136W
Coral Reef (WMV3)
28%
39%
~151W
Flight Sim. (WVC1)
55%
76%
~168W
Drag Race (WVC1)
73%
88%
~176W

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.

Video Playback Comparison
Video Clip
Diamond HD 4850
Palit HD 3870
Asus EN9600GT
Mean CPU
Peak CPU
Mean CPU
Mean CPU
Peak CPU
AC Power
Mean CPU
Peak CPU
AC Power
Rush Hour (H.264)
3%
8%
~136W
3%
9%
~105W
2%
7%
~113W
Coral Reef (WMV3)
28%
39%
~151W
27%
41%
~118W
15%
30%
~121W
Flight Sim. (WVC1)
55%
76%
~168W
50%
78%
~130W
28%
46%
~131W

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.


Available resolutions via HDMI.



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