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ASUS GeForce GTX 680 DirectCU II OC

The ASUS GeForce GTX 680 DirectCU II OC graphics card has it all: big performance, low power consumption, a very efficient and quieter cooler, and a extravagant price.

August 20, 2012 by Lawrence Lee

ASUS GeForce GTX 680
DirectCU II OC

PCI-E Graphics Card
Sample Supplier AVADirect Computers
Street Price

In January, AMD debuted their HD 7000 series GPUs, sporting the new GCN graphics core manufactured using a 28 nm process. The die-shrink combined with additional improvements resulted in sizable performance boosts without heavy increases in power draw. Their flagship Radeon HD 7970 also took the single-GPU performance crown back from the GeForce GTX 580. Nvidia’s GeForce 500 series (which is actually only a slightly modified version of the 400 series) remained viable performance-wise but as the aging 40 nm Fermi core was never terribly power efficient to begin with, the difference was now even more noticeable.

The GeForce 600 series with its 28 nm Kepler core (found in mid-high level models only) seems to address this. The high-end GTX 680 and 670 have official TDPs about 50W lower than their 500 series analogs. The new generation also provides an updated video decoder (PureVideo HD 5) capable of rendering 4K resolutions and support for four independent displays; hardcore gamers can play across three monitors using SurroundView with an extra screen keeping track of Windows desktop applications. Also, like Intel and AMD’s Turbo Boost and Turbo Core CPU overclocking technologies, the Kepler core has GPU Boost, a feature that adjusts clock speeds dynamically based on the current power draw.

The ASUS GeForce GTX 680 DirectCU II OC box.

Package contents: card, software, setup guide, SLI bridge, 2 x 6-pin to 8-pin adapter.

Our first Kepler sample is made by ASUS, the GTX 680 DirectCU II OC. “DirectCU” is a name ASUS has used many times to brand a custom down-blowing, shrouded VGA cooler. The second iteration is a behemoth with multiple heatpipes and two 10 cm fans and extends past the length of the 680’s already fairly long 26.6 cm (10.5 inch) circuit board. Like their many motherboards, the card also has ASUS’ DIGI+VRM technology, advanced voltage regulation circuitry that claims to help deliver stable, efficient power to the GPU.

The GTX 680 DirectCU II OC is currently selling for about US$530 while more barebones GTX 680’s start at US$500. You could say that this card is factory overclocked as well as its GPU Boost clock is set to 1084 MHz, about 30 MHz more than the basic model, but that figure isn’t really set in stone. If the card is running cool enough, it can and will exceed that speed. This is a card for deep-pocketed users seeking extremely smooth gameplay on monstrous 2560×1440 displays or multi-monitor configurations.

ASUS GeForce GTX 680 DirectCU II OC
(GTX680-DC2O-2GD5): Specifications

(from the product
web page
Graphics Engine
NVIDIA GeForce GTX 680
Bus Standard
PCI Express 3.0
Video Memory
Engine Clock
GPU Boost Clock : 1084 MHz
GPU Base Clock : 1019 MHz
Memory Clock
6008 MHz ( GDDR5 )
Memory Interface
DVI Output : Yes x 1 (DVI-I), Yes x 1 (DVI-D)
HDMI Output : Yes x 1
Display Port : Yes x 1 (Regular DP)
1 x Power cable
1 x Extended SLI cable
ASUS Utilities & Driver
ASUS Features
DirectCU Series
Super Alloy Power
11.8 ” x 5.1 ” x 2.3 ” Inch
*To have the best cooling performance, ASUS GTX680-DC2O-2GD5 extends the fansink to 2.5 slots. Please double check you Chassis and Motherboard dimension prior to purchase to make sure it fits in your system!

*Note that the actual boost clock will vary depending on actual system conditions. For more information, please visit http://www.geforce.com/


The ASUS GTX 680 DirectCU II OC has a hefty dual fan heatsink that’s so thick, the card takes up three expansion slots. The cooler alone accounts for 710 grams of the card’s total weight of 1.2 kg.

According to our measurements, the PCB is approximately 26.6 cm (10.5 inches) long but the cooler extends the total length to 29.7 cm (11.7 inches). It hangs over the side as well, making the card 9 mm wider than normal.

The heatsink is equipped with a pair of 10 cm fans with nine blades a piece.

The shroud covering the heatsink opens up near the back so air can be exhausted out of the case through vents on the expansion bracket. There are four video outputs, one DisplayPort, one HDMI, and two DVI connectors.

A series of pin-outs on the right-side edge of the PCB allow true enthusiasts to wire the card to select ASUS RoG (Republic of Gamers) motherboards, enabling them to adjust the card’s various voltages.

The GTX 680 requires both an 8-pin and 6-pin power adapter to function properly. They’re placed on the side for convenience.


Installation of a PCI-E graphics card is a very easy procedure but it’s nice to see exactly how much space the card takes up to determine case compatibility or interference with motherboard components. We also make a point to look under the hood and examine the heatsink itself.

The card extends about an inch past the edge of the motherboard tray in our modified Fractal Design Define R3 case. The hard drive cage was physically removed to make room for long cards but by the looks of it, the GTX 680 DirectCU II would have fit… if just barely. Also notice how much the card dips on the right side due to its weight.

A nice extra feature is the LED indicators for the external power ports that shine red when left unconnected. It’s a useful reminder for even the most experienced PC builder.

The trace side of the card is covered by an enormous backplate with multiple ventilation holes. It’s affixed at multiple points but only a few screws need to be removed to take off the main heatsink. The mounting holes around the GPU score are spaced 58 mm apart in a square formation.

The heatsink has five 8 mm thick direct-touch heatpipes, an excessive number considering the GPU core only makes contact with three. The aluminum fins are approximately 0.38 mm thick with 1.48 mm of separation.

The organization of the PCB components is very tidy with all the capacitors and inductors neatly arranged on the right side along with a long VRM heatsink. The memory chips are very close to the mounting holes though which might cause interference between third party coolers and their included memory heatsinks.


Our test procedure is an in-system test, designed to:

1. Determine whether the cooler is adequate for use in a low-noise system.
By adequately cooled, we mean cooled well enough that no misbehavior
related to thermal overload is exhibited. Thermal misbehavior in a graphics
card can show up in a variety of ways, including:

  • Sudden system shutdown, reboot without warning, or loss of display signal
  • Jaggies and other visual artifacts on the screen.
  • Motion slowing and/or screen freezing.

Any of these misbehaviors are annoying at best and dangerous at worst —
dangerous to the health and lifespan of the graphics card, and sometimes to
the system OS.

2. Estimate the card’s power consumption. This is a good indicator of how efficient
the card is, and it affects how hot the GPU runs. The lower the better.

3. Determine how well the card decodes high definition video.

Test Platform

GPU-Z screenshot.

Measurement and Analysis Tools

3D Performance Benchmarks (for low-end/budget graphics processors only)

Estimating DC Power

The following power efficiency figures were obtained for the
Kingwin LZP-1000
used in our test system:

Kingwin LZP-1000 Test Results
DC Output (W)
AC Input (W)

This data is enough to give us a very good estimate of DC demand in our
test system. We extrapolate the DC power output from the measured AC power
input based on this data. We won’t go through the math; it’s easy enough
to figure out for yourself if you really want to.

Ambient Noise Level

Our test system’s CPU fan is a low speed Scythe that is set to full speed at all times. The two Antec TrueQuiet 120 case fans are connected to the motherboard and are controlled using SpeedFan. Three standard speed settings have been established for testing.

VGA Test System:
Anechoic chamber measurements
System SPL@1m
System Fan Speed
High (loud)
26 dBA
1130 RPM
Med (quiet)
18 dBA
820 RPM
Low (silent)
12~13 dBA
580 RPM

When testing video cards and coolers with active cooling, the low setting will be used. For passive cards and heatsinks, all three settings will be tested to determine the effect of system airflow on cooling performance.

Video Test Suite

1080p | 24fps | ~10mbps
Rush Hour 3 Trailer 1
is a 1080p H.264 encoded clip inside an
Apple Quicktime container.


1080p | 24fps | ~22 mbps

H.264/MKV: A custom 1080p H.264 encoded clip inside an Matroska container.


720p | 24fps | ~1.2 mbps

Flash 720p: The Dark Knight Rises Official Trailer #3, a 720p YouTube HD trailer.


1080p | 24fps | ~2.3 mbps

Flash 1080p: The Dark Knight Rises Official Trailer #3, the same YouTube HD trailer in 1080p.


Testing Procedures

Our first test involves monitoring the system power consumption as well as CPU and GPU temperatures during
different states, idle, under load with Prime95 to stress the processor, and Prime95 plus FurMark to stress both the CPU and GPU simultaneously. This last state is an extremely stressful, worst case scenario test which generates
more heat and higher power consumption than can be produced by a modern video
game. If the card can survive this torture in our low airflow system, it should be
able to function normally in the vast majority of PCs. If we deem the card’s fan control to be overly aggressive, we can adjust them at our discretion.

Our second test procedure is to run the system through a video test suite featuring
a variety of high definition clips played with PowerDVD and Mozilla Firefox (for Flash video). During playback, a CPU usage graph is created
by the Windows Task Manger for analysis to determine the average CPU usage.
High CPU usage is indicative of poor video decoding ability. If the video (and/or
audio) skips or freezes, we conclude the GPU (in conjunction with the processor)
is inadequate to decompress the clip properly.

Lastly, for low-end and budget graphics cards, we also run a few gaming benchmarks to get a general idea of the GPU’s 3D performance. We don’t feel this is necessary for high-end models as there are many websites that do this in painstaking detail.


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)
CPU Load
CPU + GPU Load
Sys. Power (AC)
Sys. Power (DC)
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)
CPU Load
CPU + GPU Load
GPU Fan Speed
840 RPM
1200 RPM
1860 RPM
SPL @1m
15 dBA
17~18 dBA
27~28 dBA
Sys. Power (AC)
Sys. Power (DC)
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.


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

Both results are scaled by the efficiency of the power supply (tested
) 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.


System Measurements: VGA Test System
SPL @1m
GPU Temp
SPL @1m
GPU Temp
HIS HD 5870 Turbo
+ GELID Icy Vision
(5V / 1260 RPM)
17~18 dBA
17~18 dBA
DirectCU II OC
(manual, 1200 RPM)
17~18 dBA
AMD HD 6870
+ GELID Icy Vision
(5V / 1260 RPM)
17~18 dBA
17~18 dBA
DirectCU II OC
15 dBA
27~28 dBA
Gainward GTX 560
Ti Phantom
18 dBA
37 dBA
Ambient temperature: 24°C
Ambient noise level: 11 dBA
System noise level: 13 dBA

The GTX 680 DirectCU II OC’s cooler is an admirable performer, beating out the the HD 5870 paired with a GELID Icy Vision, one of the better aftermarket heatsinks available. To be fair, the 5870 uses about 30W more but it’s still a fairly impressive result for a stock cooling unit to even be in the same ballpark as a ~US$50 heatsink.

Video Playback

The GTX 680 features Nvidia’s latest of PureVideo HD video processing technology though its main benefit over older generations is support for 4K resolution video. Its ability to decoding more mundane 1080p H.264 and Flash video is similar to the previous GTX 500 series. Both AMD and Nvidia’s solutions render these types of media with no issues and eat up very few CPU cycles.

Power consumption during video playback greatly favored the Nvidia cards, with the HD 5870 and 6870 using about 30W more than their idle numbers. The GTX 680 on the otherhand used +6~8W, while the GTX 560 Ti stayed in the +10~12W region.

Clock Speed Comparison (Core/Memory in MHz)
Video Decode
HIS HD 5870 Turbo
AMD HD 6870
DirectCU II OC
Gainward GTX 560
Ti Phantom

After some investigation we found that the probable culprit for this discrepancy. The HD 5870 and 6870’s clock speeds didn’t decrease as much during playback as the GTX 680 and GTX 560 Ti. The AMD cards’ memory frequencies didn’t underclock at all while Nvidia’s cards downclocked to idle or close to idle levels.


The GTX 680 DirectCU II OC ships with ASUS’ GPU Tweak utility which offers fan and frequency adjustments as well as monitoring functionality. It looks suspiciously like MSI’s popular Afterburner application, though skinned with ASUS’ red and black Republic of Gamers scheme.

GPU Tweak also includes their own version of GPU-Z with the same color motif.

MP3 Sound Recordings

These recordings were made with a high
resolution, lab quality, digital recording system
inside SPCR’s
own 11 dBA ambient anechoic chamber
, then converted to LAME 128kbps
encoded MP3s. We’ve listened long and hard to ensure there is no audible degradation
from the original WAV files to these MP3s. They represent a quick snapshot of
what we heard during the review.

These recordings are intended to give you an idea of how the product sounds
in actual use — one meter is a reasonable typical distance between a computer
or computer component and your ear. The recording contains stretches of ambient
noise that you can use to judge the relative loudness of the subject. Be aware
that very quiet subjects may not be audible — if we couldn’t hear it from
one meter, chances are we couldn’t record it either!

The recording starts with 5~10 seconds of room ambiance, followed by 5~10 seconds
of the VGA test system without a video card installed, and then the actual product’s
noise at various levels. For the most realistic results, set the volume
so that the starting ambient level is just barely audible, then don’t change
the volume setting again.


According to credible gaming-oriented review sites like PC Perspective, HardwareCanucks and AnandTech, the GTX 680 is one of the fastest single GPU cards on the market, falling somewhere between AMD’s Radeon 7970 and the overclocked 7970 GHz Edition. Both the 7970 and 680 are overpowered for gaming with a 1920×1080 or 1920×1200 display. Their benefits don’t become apparent unless you use an even higher resolution or multi-monitor setup.

Given its level of performance we’re stunned by the energy efficiency of the GTX 680. Sitting idle, it used less power than the older Radeon HD 6870 and HD 5870 which were once praised for their idle frugality. On load, the GTX 680 used 203W, a ~30W advantage over the HD 5870 and the GTX 560 Ti, a much slower card that can be purchased for less than half the cost. The 680 was also the most efficient of these four cards at playing high definition video.

ASUS has a created a very cool, quiet, and efficient card that’s capable of some big performance numbers. The DirectCU II cooler with its dual 100 mm fans and thick, direct-touch heatpipes is a ringer, close in proficiency to the GELID Icy Vision, a US$50 third party heatsink. The automated fan control is a little aggressive but can be easily tweaked using software like MSI Afterburner or ASUS’ own GPU Tweak application. With a fan speed reduction, one can attain the rare combination of superb gaming performance and very quiet operation. The heatsink is overkill considering the relatively low power requirements but this is a blessing even if you’re unconcerned by noise. The extra thermal headroom allows one to take better advantage of the GTX 680’s GPU Boost overclocking capability.

The only thing we don’t like about the ASUS GTX 680 DirectCU II OC is the price-tag, currently US$530. If you’re looking to game on a very high resolution monitor or across multiple displays, it’s going to cost you, but even with such a high budget, value should still be taken into consideration. It stacks up well against more basic GTX 680s that start at US$500 but if you look across in the AMD aisle you might turn green with envy. The Radeon HD 7970 recently received a price drop making its various iterations $60~$90 cheaper than the GTX 680 DirectCU II OC. While it isn’t nearly as energy efficient, the price discrepancy is substantial. A GTX 680 might be able to make up the difference in electricity savings but to do so in a relatively short time frame would require a heavy use case in a location with high utility rates.

Our thanks to AVADirect Computers for the GeForce GTX 680 DirectCU II video card sample.

ASUS GTX 680 DirectCU II OC wins the SPCR Editor’s Choice

* * *

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AMD Radeon HD 6870 Graphics Card

GELID Icy Vision Dual Fan VGA Cooler

* * *

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