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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.
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SmartDoctor screen, ugliest UI ever?
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To test this feature out, we undervolted the card by 0.05V and checked for power/temperature differences.
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System Measurements: VGA Test System on Load
Asus EAH6850 DirectCU
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Measurement
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Stock Voltage
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1.10V (-0.05V)
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CPU Temp
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65°C
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63°C
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SB Temp
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52°C
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52°C
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GPU Core Temp
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74°C
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71°C
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GPU VRM Temp
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75°C
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72°C
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GPU Fan Speed
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2310 RPM
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2160 RPM
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SPL@1m
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17~18 dBA
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16~17 dBA
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System Power (AC)
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258W
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248W
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System Power (DC, est.)
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211W
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203W
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Ambient temperature: 23°C
IGP system noise level: 13 dBA
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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.
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Estimated Power Consumption (DC)
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Card
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Idle
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Load
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AMD HD 6850 1GB
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16W
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91W
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Asus EAH6850 DirectCU
(-0.05V)
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16W
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92W
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Asus EAH6850 DirectCU
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16W
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100W
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ATI HD 4870 1GB
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55W
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147W
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HIS HD 4890 Turbo 1GB
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57W
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153W
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AMD HD 6870 1GB
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18W
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163W
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HIS HD 5870 Turbo 1GB
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22W
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216W
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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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