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Asus DirectCU & AMD Radeon HD 6850 Graphics Cards

The Radeon HD 6850 is AMD’s sub US$200 entrant in the discrete graphics card market. We have two on the bench to compare, a reference sample from AMD, and the Asus EA6850DirectCU, which is overclocked, has an adjustable core voltage, and is cooled using a direct-touch heatpipe heatsink. They turn out to be winners, especially the Asus.

December 5, 2010 by Lawrence Lee

AMD Radeon HD 6850
PCI-E Graphics Card
Asus EAH6850 DirectCU
PCI-E Graphics Card
Street Price

Nvidia and AMD are always dueling for graphics supremacy, but like Intel and AMD, the one with the fastest chip — regardless of the rest of the product lineup — is usually crowned the king by the media. While great for publicity, the fastest and most expensive graphics card can only be afforded by a few, and actually purchased by even fewer.

It is fun to see just how high and far technology has come, but we reserve much of our praise for the more reasonable, affordable chips and boards, the ones that deliver great value, not ultimate performance. GPUs like the US$500+ GeForce GTX 580 make for big headlines, but it’s blue-collar grunts like the GeForce GTX 460 that have more of an impact on the overall market. When it came time to debut the HD 6000 series, AMD didn’t rush out a high-end model; instead they released two midrange cards. The aim was to offer competitive alternatives to the GTX 460 and fill in some of AMD’s gaps in the juicy center of the market.

The AMD Radeon HD 6850.

The Asus EAH6850 DirectCU.

We’ve already taken a look at the HD 6870, and now it’s the HD 6850’s turn. We have two of them, a reference model from AMD, and the Asus EAH6850 DirectCU. The latter name comes from its cooler, which uses direct-touch heatpipes composed of copper (CU is copper’s symbol on the periodic table of elements). Not only does it have an interesting heatsink, the card is factory overclocked, and has the potential to be 50% faster according to Asus, thanks to the “Voltage Tweak” ability printed on the card’s packaging and literature. The GPU core voltage can be easily changed by overclockers looking for a free performance boast.



The reference HD 6850 came as a bare card only, while the EAH6850 DirectCU was shipped to us in a larger than necessary retail box. While a little extra room is required for accessories, unless there is a second card in there, the packaging does not need to be this excessive.

The improvements brought to the table by the new Barts core in the HD 6000 series has been covered in our Radeon HD 6870 review. From a technical standpoint, the HD 6850 is a slightly cut-down version of the 6870. The 6870 has core/memory speeds of 900/1050 MHz and 1120 stream processors, while the 6850 runs at 775/1000 MHz with 960 stream processors. The Asus EAH6850 DirectCU is slightly overclocked with a 15 MHz bump in core frequency.

Specifications: Asus EAH6850 DirectCU
(from the product web page)
Graphics Engine AMD Radeon HD 6850
Bus Standard PCI Express 2.1
Video Memory GDDR5 1GB
Engine Clock 790 MHz
Memory Interface 256-bit
Resolution D-Sub Max Resolution : 2048×1536
DVI Max Resolution : 2560×1600
Interface D-Sub Output : Yes x 1 (via DVI to D-Sub adaptor x 1)
DVI Output : Yes x 1 (DVI-I),Yes x 1 (DVI-D)
HDMI Output : Yes x 1
Display Port : Yes x 1
HDCP Support : Yes
Accessories 1 x DVI to D-Sub adaptor
1 x CrossFire cable
1 x Power cable
Software ASUS Utilities & Driver
ASUS Features DirectCU Series
Dimensions 10.24 ” x 4.84 ” Inch


The AMD Radeon HD 6850 is a dual slot graphics card with a length of 22.9 cm (9.0″), making it slightly shorter than the HD 6870. The reference cooler appears identical: An enclosed box style unit with a blower fan pushing air over an internal heatsink and out the back.

A large number of screws on the back as well as a couple on the PCI bracket must be removed to detach the stock heatsink.

The 6850’s memory and VRM cooling plate is not attached to the main heatsink and shroud. Also, the VRMs are located on the right side of the GPU core while the pictures of every retail 6850 we’ve seen show them on the left side. The GPU core is also shifted toward the left side, similar to the HD 5770 / 5850.

Like the 6870 reference cooler, the cooling plate has a big tab sticking out on one side that may interfere with some aftermarket coolers.

One of the MOSFETs was not making any contact with the cooling plate because a thermal pad was missing. This was not discovered until after testing but it did not seem to cause any stability issues. We patched it afterwards with some trimmings excised off the memory chips’ pads.

The 6870 reference heatsink has a thick copper base, three large heatpipes, and a block of aluminum fins twice the size of the 6850’s. This cooler uses a vapor chamber, essentially a very large, flattened heatpipe that transfers heat in a similar manner. It is said to transfer heat far more effectively than a solit piece of copper the same size.

It looks like a thin copper base soldered to a small stack of aluminum fins, but this combination would be completely inadequate. It’s an odd choice for the 6850 as the only reference coolers we know of utilizing vapor chambers are those employed on top-end GPUs like the HD 5970 and GTX 580.


The Asus EAH6850 DirectCU is a dual slot graphics card half an inch longer than the reference card. The PCB measures 23.8 cm, but the cooler’s shroud extends the length to 24.1 cm (9.5′). Like many third party manufacturers, Asus went with a down-blowing heatsink model.

The accessories include the usual suspects with one odd extra: a CD wallet. Obviously the box could’ve been reduced in size significantly.

The fan has a wingspan of 73 mm and is is designed to blow downward with the shroud helping direct air across the PCB. The heatpipes extend over the edge of the card by 11 mm.

Though there is a small vent on the PCI bracket, the cooler doesn’t push air out the back. In most cases it will act as an intake.

Two direct-touch heatpipes contacting the GPU core are visible from the side.

Notice the metal strip running along the outside of the card. Its seems to serve no other purpose except to provide structural integrity to the circuit board.


With only four screws holding it to the card, the Asus EAH6850 DirectCU heatsink is much easier remove. The main heatsink is much larger than the reference model, and has a pair of direct-touch heatpipes.

Two heatpipes isn’t a lot in this day and age, but with the direct-touch method, it’s just right. The core of the HD 6850 is too small to take advantage of more.

The heatpipes are 8 mm thick and nickel-plated, at least on the outside. The portion on the underside is less likely to oxidize, and to make matter contact with the core, had to be sanded down.

The plastic cover is screwed down to the heatsink at several points, including an inaccessible location just under the mounting plate. It cannot be removed without damaging the cooler unless you have a perpendicular screw driver handy.

A small VRM heatsink is attached using a pair of pushpins and a thermal pad.

Our sample had bare 1.5 ns Hynix memory chips rated for 1.25 GHz, 25% higher than stock.


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 will have an effect on how hot the stock cooler becomes due
to power lost in the form of heat. The lower the better.

Test Platform

AMD Radeon HD 6850 technical specifications according to GPU-Z.

Asus EAH6850 DirectCU technical specifications according to GPU-Z.

Measurement and Analysis Tools

Estimating DC Power

The following power efficiency figures were obtained for the
Seasonic S12-600
used in our test system:

Seasonic S12-500 / 600 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.

H.264/VC-1 Test Clips

H.264 and VC-1 are codecs commonly used in high definition movie videos
on the web (like Quicktime movie trailers and the like) and also in Blu-ray
discs. To play these clips, we use Cyberlink PowerDVD.

1080p | 24fps | ~10mbps
1080p H.264:
Rush Hour 3 Trailer 2c
is a 1080p clip encoded in H.264
inside an Apple Quicktime container.


1080p | 24fps | ~8mbps
Coral Reef Adventure Trailer
is encoded in VC-1 using
the WMV3 codec commonly recognized by the “WMV-HD” moniker.

x264/MKV Video Test Clip

MKV (Matroska) is a very popular online multimedia container
used for high definition content, usually using x264 (a free, open source
H.264 encoder) for video. The clip was taken from a full length movie;
the most demanding one minute portion was used. We use Media Player Classic
Home – Cinema to play it as its default settings allow it to use DXVA
(DirectX Video Acceleration) by default.

1080p | 24fps | ~14mbps

x264 1080p: Spaceship is a 1080p x264 clip encoded from
the Blu-ray version of an animated short film. It features a
hapless robot trying to repair a lamp on a spaceship.

Testing Procedures

Our first test involves recording the system power consumption using a Seasonic
Power Angel as well as CPU and GPU temperatures using SpeedFan and GPU-Z during
different states: Idle, under load with CPUBurn running to stress the processor,
and CPUBurn plus FurMark running 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 it can survive this torture in our low airflow system, it should be
able to function nominally in the majority of PCs.

If the heatsink has a fan, the load state tests are repeated at various fan
speeds (if applicable) while the system case fan is left at its lowest setting
of 7V. If the card utilizes a passive cooler, the system fan is varied instead
to study the effect of system airflow on the heatsink’s performance. System
noise measurements are made at each fan speed.

Our second test procedure is to run the system through a video test suite featuring
a variety of high definition clips. 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. Power consumption during playback
of high definition video is also recorded.


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

System Measurements:
VGA Test System (IGP)
CPU Temp
SB Temp
13 dBA
System Power (AC)
System Power (DC, est.)
Ambient temperature: 22°C
Ambient noise level: 11 dBA

AMD Radeon HD 6850

System Measurements: VGA Test System with
Reference AMD Radeon HD 6850
CPUBurn + FurMark
CPU Temp
SB Temp
GPU Core Temp
GPU Fan Speed
810 RPM
1880 RPM
14 dBA
23 dBA
System Power (AC)
System Power (DC, est.)
Ambient temperature: 23°C
IGP system noise level: 13 dBA

The stock AMD 6850 cooler does a fairly good job keeping things cool. The GPU core stabilized at 83°C, which is quite low for a modern graphics card. As it pushes exhaust out the back of the card, system temperatures remained moderate even on full load.

The system noise level was an impressive 14 dBA@1m when idle, a barely audible difference over the same system running without a video card. On load, the fan increased in speed by about 1000 RPM, generating an increase of 9 dB. It had an unappealing buzz, but the overall noise level was pretty good compared to most stock graphics cards. The fan is a little over-aggressive, in our opinion.

Cooling was very good despite the small size of the heatsink utilized by AMD; its efficiency is impressive.

Asus EAH6850 DirectCU

System Measurements: VGA Test System with
Asus EAH6850 DirectCU
CPUBurn + FurMark
CPU Temp
SB Temp
GPU Core Temp
GPU Fan Speed
1560 RPM
2310 RPM
15 dBA
17~18 dBA
System Power (AC)
System Power (DC, est.)
Ambient temperature: 23°C
IGP system noise level: 13 dBA

The Asus EAH6850 DirectCU is well cooled as well, though on load, system temperatures were much higher, as there is no direct escape path for the hot air radiating off the card. As a result both the nearby southbridge and CPU saw higher temperatures. The GPU was well taken care of, stabilizing at only 75°C on load; the fan could have been slowed down a bit without much risk.

From a noise perspective, the EAH6850 DirectCU is one of the quietest cards we’ve ever tested, generating only 15 dBA@1m when idle and 17~18 dBA@1m on load in our VGA test system. At idle, its acoustics were dominated by a quiet, but audible low frequency hum. On load, it actually sounded slightly better subjectively as the hum was masked by the broadband sound of increased air turbulence.


System Measurements: VGA Test System on Load
AMD/Asus HD 6850 vs. AMD HD 6870
AMD Radeon HD 6850
Asus EAH6850 DirectCU
AMD Radeon HD 6870
CPU Temp
SB Temp
GPU Core Temp
GPU Fan Speed
1880 RPM
2310 RPM
2950 RPM
23 dBA
17~18 dBA
34 dBA
System Power (AC)
System Power (DC, est.)
Ambient temperature: 23°C
IGP system noise level: 13 dBA

The practical difference between the two coolers boils down to GPU vs. system cooling. The DirectCU heatsink is far superior at cooling the video card, producing better GPU temperatures with lower noise levels. The reference heatsink dumps a lot of the heat outside the case resulting in better CPU and southbridge cooling.

On load, the noise difference between the two cards is significant.

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
Stock Voltage
1.10V (-0.05V)
CPU Temp
SB Temp
GPU Core Temp
GPU Fan Speed
2310 RPM
2160 RPM
17~18 dBA
16~17 dBA
System Power (AC)
System Power (DC, est.)
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

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. 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)
AMD HD 6850 1GB
Asus EAH6850 DirectCU
Asus EAH6850 DirectCU
ATI HD 4870 1GB
HIS HD 4890 Turbo 1GB
AMD HD 6870 1GB
HIS HD 5870 Turbo 1GB

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.

Clocks & Voltages

Using Radeon BIOS Editor, we examined the BIOS used by both the AMD and Asus Radeon HD 6850. This revealed how each card handles clock/voltage settings in various states.

Clock/Voltage Settings
AMD Radeon HD 6850
Asus EAH6850 DirectCU
775/1000 MHz, 1.10V
775/1000 MHz, 1.15V
Low (idle)
100/300 MHz 0.95V
100/300 MHz, 0.95V
UVD (video playback)
300/1000 MHz, 0.95V
300/1000 MHz, 0.95V
600/1000 MHz, 1.00V
600/1000 MHz, 1.10V
High (load)
775/1000 MHz, 1.10V
790/1000 MHz, 1.15V

The power difference between the two cards on load is explained simply by the difference in Vcore. The reference Radeon HD 6850 runs at 1.10V with a core clock speed of 775 MHz during boot-up and on load. The EAH6850 DirectCU uses an extra 0.05V, and on load, it is overclocked by 15 MHz. The idle and UVD settings are identical.

Fan Control

AMD and Asus DirectCU Radeon HD 6850 BIOS fan control settings.

Both cards had the same BIOS fan control settings. When the system is turned on, the GPU fan spins up briefly at 70% speed, then stays at 22% until the core temperature reaches 55°C. The duty cycle increases linearly until it tops out at 100% at 102°C.

Asus’ SmartDoctor utility as well as MSI Afterburner can be used to adjust each card’s fan speeds. However, during our testing both cards ran at the minimum fan speed when idle, so it is impossible to lower the idle noise level through conventional means.


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.


Gaming: Please check out gaming-oriented reviews of the HD 6870 at sites
like like HardwareCanucks,
The Tech Report, and
AnandTech. The general
consensus is that the HD 6850 performs well enough to compete with the slightly more expensive 1GB version of the GeForce GTX 460, and is arguably the best midrange GPU you can buy for under US$200.

Power Consumption: By our estimates, both the reference AMD Radeon HD 6850 and Asus EAH6850 DirectCU use only 16W when idle, a small improvement over the AMD Radeon HD 6870. On load, the reference card consumed 91W, while the slightly overclocked/overvolted Asus version used 100W (though with a slight voltage tweak, it draws almost even). Both numbers are excellent considering the performance delivered by the HD 6850. Most users will not require a big power supply upgrade to use either card.

Cooling: When idle, the stock heatsinks on both cards are very quiet, even by SPCR standards, with the reference model coming out slightly ahead; it is just a little bit quieter and smoother sounding. On load, the reference cooler is much louder, emitting 6~7 dB more than the amazingly quiet Asus DirectCU cooler. Our test system with the Asus card installed measured only 17~18 dBA@1m and the heatsink kept the GPU substantially cooler. However you can expect higher system temperatures with the Asus card in a traditional tower case as it does not exhaust air out the back like the reference cooler.

The AMD Radeon HD 6850 is energy efficient and relatively quiet for a reference card, though the fan speed is higher than it needs to be on load. It is rather odd though that a midrange card would be equipped with a vapor chamber heatsink rather than traditional heatpipes. The board layout is also different than every retail HD 6850 we’ve seen online. Furthermore, only a few of AMD’s partners are using side-blowing exhaust style coolers; the vast majority are utilizing down-blowing heatsinks. It is beyond weird that no one is following this so-called reference design.

The Asus EAH6850 DirectCU is one of the best-cooled and quietest graphics cards we have come across in a long time. Though the heatsink doesn’t look like much, its direct-touch heatpipes do an excellent job, allowing the fan to spin at fairly low speeds. It could even be quieter if Asus departed from the reference fan profile; end-users can use a variety of software utilities to make the EAH6850 DirectCU even quieter on load. Asus has also allowed users to play with the core voltage in both directions. You can undervolt to trim power consumption, heat, and noise, or you can overvolt it to reach higher clock speeds for better performance. At US$190, it is priced slightly higher than the cheapest HD 6850’s, but it’s worth the premium in our opinion. Its noise level is excellent, and you can tweak it for whatever purposes suits you.

Our thanks to AMD and Asus for the reference Radeon HD 6850 and Asus EAH6850 DirectCU samples.

* * *

Asus EAH6850 DirectCU

SPCR Editor’s Choice Award

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