Asus DirectCU & AMD Radeon HD 6850 Graphics Cards

Graphics Cards
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Asus EAH6850 DirectCU: Voltage Adjustment

One further advantage of the EAH6850 DirectCU over the reference counterpart are voltage tweak features that can aid in overclocking. Vcore can be changed from 0.95V to 1.35V (the default is 1.15V). This adjustment can be made using the Asus Smart Doctor utility.


SmartDoctor screen, ugliest UI ever?

To test this feature out, we undervolted the card by 0.05V and checked for power/temperature differences.

System Measurements: VGA Test System on Load
Asus EAH6850 DirectCU
Measurement
Stock Voltage
1.10V (-0.05V)
CPU Temp
65°C
63°C
SB Temp
52°C
52°C
GPU Core Temp
74°C
71°C
GPU VRM Temp
75°C
72°C
GPU Fan Speed
2310 RPM
2160 RPM
SPL@1m
17~18 dBA
16~17 dBA
System Power (AC)
258W
248W
System Power (DC, est.)
211W
203W
Ambient temperature: 23°C
IGP system noise level: 13 dBA

A quick test at load shows that the voltage change did take, resulting in slightly lower temperatures, decreased GPU fan speed and noise level, and a drop in power consumption. Changes in voltage only seemed to apply at load though. We observed no changes in power consumption when the system sits idle.

Power Consumption

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 idle. 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.

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. 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.

Note: the actual power of the add-on card cannot be derived using this method because the integrated graphics may draw some power even when not in use. If we assume our old test system with GMA 950 graphics used 1~2W, we estimate that the integrated HD 4200 graphics chip in our new setup uses 2W more than that, based on tests conducted using a low-end reference card. However, the relative difference between the cards should be accurate.

Estimated Power Consumption (DC)
Card
Idle
Load
AMD HD 6850 1GB
16W
91W
Asus EAH6850 DirectCU
(-0.05V)
16W
92W
Asus EAH6850 DirectCU
16W
100W
ATI HD 4870 1GB
55W
147W
HIS HD 4890 Turbo 1GB
57W
153W
AMD HD 6870 1GB
18W
163W
HIS HD 5870 Turbo 1GB
22W
216W

Like the HD 6870, both of our HD 6850 samples consume very little power when idle, about 16W by our estimates. The reference model pulled approximately 91W on load, while the Asus' DirectCU version consumed about 9W more, though this can be equalized by tweaking the core voltage.

The HD 4000 series by comparison seem terribly inefficient, with the HD 4870 and 4890 gobbling up more than three times as much energy when idle and 50% more on load, despite offering poorer performance.

Power consumption and CPU usage during video playback was very similar to the HD 6870.



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