ASUS GeForce GTX 680 DirectCU II OC

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TEST RESULTS

Baseline with Integrated Graphics: First, here are the results of our baseline results of the system with its integrated graphics, without a discrete video card. We also need the power consumption reading during Prime95 to estimate the actual power draw of the discrete card later.

Power Consumption Measurements:
VGA Test System (IGP)
Measurement
Idle
CPU Load
CPU + GPU Load
Sys. Power (AC)
36W
74W
87W
Sys. Power (DC)
unknown
61W
72W
System fan speeds: low (580 RPM)
Ambient noise level: 10~11 dBA
System noise level: 12~13 dBA

System with ASUS GTX 680 DirectCU II OC:

System Measurements: VGA Test System
(ASUS GTX 680 DirectCU II OC)
State
Idle
CPU Load
CPU + GPU Load
Temp
CPU
27°C
42°C
62°C
61°C
PCH
43°C
44°C
61°C
57°C
GPU
34°C
34°C
85°C
75°C
GPU VRM
49°C
50°C
112°C
96°C
GPU Fan Speed
840 RPM
(auto)
1200 RPM
(manual)
1860 RPM
(auto)
SPL @1m
15 dBA
17~18 dBA
27~28 dBA
Sys. Power (AC)
58W
99W
281W
280W
Sys. Power (DC)
unknown
84W
265W
264W
System fan speeds: low (580 RPM)
Ambient noise level: 10~11 dBA
Ambient system noise level: 12~13 dBA
Ambient temperature: 24°C

Note: the GPU Boost feature clocked the core at 1111 MHz during both load states, eclipsing the officially specified 1084 MHz figure.

The GTX 680 DirectCU II OC was very quiet under idle conditions. The GPU fan spun at only 840 RPM and our test system measured 15 dBA@1m, only 2~3 dB higher than what the system produces running without a discrete video card. On load we found that the fan speed behavior was overly aggressive, pumping up the fan to 1860 RPM to maintain a GPU temperature of 75°C and generating a noise level of 27~28 dBA@1m. Taking the fan off automatic control, we found that even 1200 RPM was sufficient and a great deal quieter.

System power consumption was an impressively low 60W AC when sitting idle while load pushed it to to 281W. The latter figure is still very reasonable considering the GTX 680 is a top tier performer with a US$500+ price-tag. It does produce a considerable amount of heat however as stressing the GPU heated up the CPU by an additional 20°C, an increase 5°C greater than putting the CPU on load by itself. The GPU cooler is very good at keep the video card cool but as it lacks a side-blowing fan, a good amount of exhaust is required to keep heat from lingering in the upper portion of the case.

The quality of noise generated by the GTX 680 DirectCU II OC was quite good. Sitting idle, the test system had a very gentle hum that was difficult to pick out compared to the same machine running without a dedicated graphics card. On load with the fan spinning at 1860 RPM, there were some tonal elements that we could detect up close, but at one meter's distance, the turbulent noise from the fans and the side panel of the case masked it fairly well.

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 Prime95 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 Prime95 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 Prime95 and FurMark running simultaneously. Then the power of the baseline system (with integrated graphics) running just Prime95 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. However, the relative difference between the cards should be accurate.

With an estimated idle power of 23W, the GTX 680 DirectCU II OC is one of the most efficient performance cards we've tested, beaten only by the Gainward GTX 560 Ti. The GTX 680 is also very frugal on load, using just over 200W, a full 30W less than the much slower GTX 560 Ti and an overclocked Radeon HD 5870.



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