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ASUS Radeon HD 7870 DirectCU II

The ASUS Radeon HD 7870 DirectCU II is a high-end graphics card with a large dual fan cooler. Though it has an impressive look, it doesn’t have quite what it takes to cool the GPU quietly at full load.

October 15, 2012 by Lawrence Lee

Product
ASUS HD 7870 DirectCU II
HD7870-DC2-2GD5-V2

PCI-E Graphics Card
Manufacturer
ASUS
Street Price
US$240

Recently we reviewed the ASUS GeForce GTX 680 DirectCU II OC, a top-of-the-line graphics card with a large and impressive dual fan heatsink. While it’s a superb video card, as with most cutting-edge PC hardware, it’s a prime example of diminishing returns on investment. The more you pay, the less improvement you get; a US$460 GTX 680 unfortunately doesn’t offer twice as much performance as a card half the price like the Radeon HD 7870. Slower cards tend to almost always give you more bang for your buck until you hit the sweet spot which is actually somewhere around the US$100 mark.

High-End Radeon HD 7000 Comparison
Model
HD 7850
HD 7870 GHz Edition
HD 7950
HD 7970
Transistor Count
2.8 billion
2.8 billion
4.3 billion
4.3 billion
Die Size
212 sq. mm
212 sq. mm
352 sq. mm
352 sq. mm
Shader Units
1024
1280
1792
2048
Core Frequency
860 MHz
1000 MHz
800 MHz
925 MHz
Memory Type
1GB / 2GB GDDR5
2GB GDDR5
3GB GDDR5
3GB / 6GB GDDR5
Memory Frequency
1200 MHz
1200 MHz
1250 MHz
1375 MHz
Memory Bus
256-bit
256-bit
384-bit
384-bit
TDP
130W
175W
200W
250W
Street Price (USD)
$170 / $190
$230
$300
$380 / $600

The HD 7870 doesn’t represent the best value available but it certainly offers more than it did at release. Launched in March with a MSRP of about US$350, the HD 7870 has since tumbled in price by more than US$100 though it still occupies a mid-to-high position in AMD’s Radeon HD 7000 lineup. Based on AMD’s 28 nm “Pitcairn” architecture, the 7870 die is packed with with 1280 stream processors and a 256-bit memory interface. The reference model calls for a core clock speed of 1000 MHz (making it a “GHz Edition”, a seemingly superfluous naming convention) and 2GB of GDDR5 1200 MHz, to which our ASUS HD 7870 DirectCU II sample conforms.


The ASUS HD 7870 DirectCU II.

Though “DirectCU II” is printed clearly on the box and heatsink shroud, it isn’t the same bulky cooler found on the GTX 680 DirectCU II OC. The moniker describes the style of cooler ASUS uses on most of their cards to differentiate it from reference cooling solutions — it’s not a single, distinctive heatsink model. Compared to the GTX 680’s heatsink, this is a much smaller cooling solution, taking up only two slots in total as the fans are substantially thinner. The layout is also completely flipped around, with fins running down the length of the board rather than widthwise, and heatpipes intersecting them on the perpendicular.

ASUS Radeon HD 7870 GHz Edition Model Comparison
Model
HD7870-DC2-2GD5
HD7870-DC2-2GD5-V2
HD7870-DC2T-2GD5
HD7870-DC2TG-2GD5-V2
Core Clock
1010 MHz
1000 MHz
1100 MHz
1100 MHz
Memory Clock
1210 MHz
1200 MHz
1250 MHz
1250 MHz
Outputs
2 x Mini-DP, HDMI, DVI
DP, HDMI, 2 x DVI
2 x Mini-DP, HDMI, DVI
DP, HDMI, 2 x DVI
Additional Features
N/A
DIGI+ VRM
N/A
DIGI+ VRM
Extras
CF cable, VGA adapter,
CF cable, VGA adapter
CF cable, VGA adapter, power cable
CF cable, VGA adapter, Diablo III mouse pad

To befuddle consumers, ASUS is currently offering four separate versions of the HD 7870 with minor variations in the model number to differentiate them. The D2T‘s are clocked higher than the DC2‘s, at 1100/1250 MHz, while the V2 editions have more advanced voltage regulation circuitry (DIGI+VRM) and trade two mini-DisplayPorts for one regular DisplayPort and an additional DVI connection. Our sample is the HD7870-DC2-2GD5-V2 (in bold in the table above).

ASUS HD 7870 DirectCU II (HD7870-DC2-2GD5-V2): Specifications (from the product
web page
)
Graphics Engine
AMD Radeon HD 7870
Bus Standard
PCI Express 3.0
Video Memory
GDDR5 2GB
Engine Clock
1000 MHz
Memory Clock
4800 MHz ( 1200 MHz GDDR5 )
RAMDAC
400 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-D), Yes x 1 (DVI-I)
HDMI Output : Yes x 1
Display Port : Yes x 1 (Regular DP)
HDCP Support : Yes
Accessories
1 x CrossFire cable
1 x DVI to D-Sub adaptor
Software
ASUS Utilities & Driver
ASUS Features
DirectCU Series
Dimensions
01.47 ” x 4.25 ” x 1.54 ” Inch

PHYSICAL DETAILS

The ASUS HD 7870 DirectCU II is 24.1 cm long measured from the rear panel to the far edge of the circuit board and the cooler adds an additional 2.3 cm to its length. The heatpipes also hang over the edge of the PCB, increasing its effective width by 2.0 cm. The heatsink accounts for 440 grams of the card’s 710 gram total weight.


The card is equipped with a large, dual fan VGA cooler, but this particular specimen is unimpressive due to its very thin 80 mm fans. The larger three-slot GTX 680 DirectCU II OC cooler used full sized fans.


Video outputs: DVI-I, DVI-D, HDMI, DisplayPort.


The cooler is secured using the standard 53 mm square, four screw arrangement found on most Radeons produced in the past few years. If you go with a heavy aftermarket cooler, there’s a metal strip running along the outside edge of the PCB that helps keep the card from bending.


The heatsink uses 3 x 8 mm thick direct touch heatpipes to transfer heat to the aluminum fins which are about 0.40 mm thick and spaced 1.40 mm apart. Strangely, a thermal pad near the base helps cool only four of the eight memory chips while the other four are left bare. The fans are powered off a small 5-pin connector; we’re not sure what the 5th pin is for.


The PCB layout is very clean with all the capacitors and inductors off to the sides. The GPU core is positioned nearly dead center.

TEST METHODOLOGY

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

GPUs Compared:

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)
65.5
90.7
149.0
199.6
251.2
300.3
400.9
AC Input (W)
81
105
166
211
265
322
426
Efficiency
80.8%
86.4%
89.8%
92.8%
92.9%
93.5%
94.1%

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.

GPU Test System:
Anechoic chamber measurements
Setting
System Fan Speed
System SPL@1m
High (loud)
1130 RPM
26 dBA
Med (quiet)
820 RPM
18 dBA
Low (silent)
580 RPM
12~13 dBA
Note: mic is positioned at a distance of one meter from the center of the case’s left side panel at a 45 degree angle.

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 | ~22 mbps

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

 


1080p | 24fps | ~2.3 mbps

Flash 1080p: The Dark Knight Rises Official Trailer #3, a 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. Noise levels are measured and recorded as well; if we deem the card’s fan control to be overly aggressive, we can adjust them at our discretion using various software tools.

Our second test procedure is to run the system through a video test suite featuring
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.

GPU Cooler Testing

Heatsink testing requires only the Prime95 plus FurMark stress test to be used. The fan(s) (if applicable) are connected to a custom external fan controller and tested at various speeds to represent a good cross-section of its airflow and noise performance.

Our GPU cooler test card is an HIS Radeon HD 5870 iCooler V Turbo, a factory-overclocked single GPU card that draws about 236W by our estimates. The stock VRM heatsink is left on for convenience.

TEST RESULTS

Baseline Power with Integrated Graphics:

Power Consumption Measurements:
GPU Test System (Intel HD 2000 IGP)
State
Idle
CPU Load
CPU + GPU Load
Sys. Power (AC)
36W
74W
87W
Sys. Power (DC)
unknown
61W
72W
System fan speeds: Low
Ambient noise level: 10~11 dBA
System noise level: 12~13 dBA

System with Discrete Graphics:

System Measurements: GPU Test System
(ASUS HD 7870 DirectCU II)
State
Idle
CPU Load
CPU + GPU Load
Temp
CPU
21°C
38°C
56°C
PCH
34°C
41°C
51°C
GPU
31°C
33°C
91°C
GPU VRM
43°C
45°C
93°C
GPU Fan Speed
1080 RPM
3240 RPM
SPL @1m
14 dBA
30~31 dBA
Sys. Power (AC)
50W
90W
264W
Sys. Power (DC)
unknown
75W
250W
Ambient noise level: 10~11 dBA
System noise level on integrated graphics: 12~13 dBA
Ambient temperature: 22°C

With our test system fans on our low speed, 12~13 dBA@1m setting, the HD 7870 DirectCU II ran fairly cool and quiet when idle. The fans were spinning at 1080 RPM but they barely made a dent in the overall SPL and the power draw was only 50W AC which is excellent for a high-end GPU. Putting the system on CPU load had only a 2°C impact on the GPU temperature. The addition of a GPU load pushed the fans to 3240 RPM for a total noise level of 30~31 dBA@1m. The fan control wasn’t being overly aggressive though as this measurement was taken after the GPU core had stabilized at 91°C. It was loud, but needed to be to keep the card adequately cooled.

If you only care about idle noise, the HD 7870 DirectCU II is a great choice. Compared to the GPU test system without discrete graphics, the noise level was only 1~2 dB higher, with most of the extra output limited to the 200~500 Hz range. Subjectively, the overall sound was indistinguishable.

On load, the cooler was much louder of course but it also took on a more complex and undesirable acoustic character. The fans became quite whiny and there was also a clearly audible low frequency hum which explains the incredibly sharp tonal peak we observed at ~220 Hz. It doesn’t sound great but we’ve definitely encountered worse.

Noise & Cooling Comparison

Comparison: GPU Test System (Load)
Model
Est. Power Draw (DC)
GPU Temp
SPL @1m
HIS HD 5870 Turbo
GELID Icy Vision @5V
236W
89°C
17~18 dBA
AMD HD 6870 +
GELID Icy Vision @5V
182W
80°C
17~18 dBA
ASUS GTX 680
DirectCU II OC
203W
75°C
27~28 dBA
ASUS HD 7870
DirectCU II
189W
91°C
30~31 dBA
Gainward GTX 560
Ti Phantom
233W
88°C
37 dBA
System fans on low (12~13 dBA@1m).
Ambient temperature: 22°C

You would expect a dual fan cooler to produce good results but the 7870 is quite power hungry and the DirectCU II heatsink is equipped with rather thin fans. The end result is a rather high GPU temperature and noise level compared to what you’d get with an aftermarket cooler. The GELID Icy Vision paired with a HD 5870, which has a much higher power draw, managed to keep the GPU temperature under 90°C while generating an overall system SPL of only 17~18 dBA@1m.

The ASUS GTX 680 DirectCU II OC has a similar looking heatsink to the HD 7870, but it’ much larger, with more heatpipes and full-sized fans, and it too, was quieter and cooler despite using more power. That being said, the GTX 680 is about double the price of the HD 7870 so it perhaps is more deserving of a beefed up cooling solution.

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 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.

According to our calculations, the HD 7870 DirectCU II consumed about 14W when idle and 189W on full synthetic load. Its load draw is very close to the HD 6870 but it uses almost half as much energy when idle. It’s supposed to be a much faster card though, so these figures are fairly impressive.

Like many previous high-end Radeon graphics cards, playing hardware-accelerated HD video wasn’t nearly as efficient. Measured from the wall, our HD 7870-equipped GPU test system consumed 83W when playing high definition H.264 and Flash video compared to 50W when idle. The culprit seemed to be high clock speeds when the HD 7870’s UVD chip was activated, a common issue we’ve had with past AMD video cards. According to GPU-Z, its core/memory speeds were 450/1250 MHz compared to 300/150 MHz when idle.

All of the AMD/NVIDIA cards from the last three generations had very similar CPU usage during video playback, 1~2% for our 1080p H.264/MKV test clip, and 8~9% for our YouTube HD sample — the 7870 was no exception.

MP3 Sound Recording

This recording was 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. It’s intended to give you an idea of how our test system 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 GPU test system with its case fans at various speeds. 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.

FINAL THOUGHTS

According to credible gaming-oriented review sites like PC Perspective, HardwareCanucks and AnandTech, the HD 7870 is a high-end graphics card that can play most titles smoothly at 1920×1200 resolution with maximum detail, and can comfortably render even higher resolutions if you knock down the image quality settings a few rungs. The general consensus is that it’s roughly 20% faster than the HD 7850 (~US$180) and trades blows with the GeForce GTX 660 (~US$230) with the HD 7870 prevailing slightly at higher resolutions. These two cards seem to offer the best value in the US$200~$300 price range. The HD 7950 delivers an additional 10% performance boost for ~US$300.

The cooler used on the ASUS Radeon HD 7870 DirectCU II looks more impressive than it is. In 2D operation, it’s very quiet and should be completely inaudible in most systems, but with a GPU load it gets quite loud. The fan control behavior is set to prevent the GPU temperature from exceeding about 90°C so it’s not overly aggressive either. The heatsink is designed for high airflow but the fans are a little undersized and probably don’t do it justice as a result. We would classify its cooling performance as adequate but nothing more. If you’re looking for better, potentially quieter cooling from a stock unit, Sapphire and PowerColor have 7870’s with larger fans and Gigabyte offers a massive triple fan model.

The card’s energy efficiency is excellent except when playing video. We estimated the power draw to be only 14W when idle, easily the lowest we’ve seen from a high-end card in some time. On load, it consumed about 189W, a modest amount by today’s standards considering its level of performance. During both Flash and H.264 1080p playback, the power draw was 33W higher than at idle, 15~20W more than the GeForce 560 Ti and GTX 680 — NVIDIA seems to have the advantage in this department. If you watch a lot of video and your system supports Lucid’s Virtu technology, you may want to try using the IGP for video decoding to save power.

Our thanks to ASUS for the HD 7870 DirectCU II video card sample.

* * *

Articles of Related Interest
Prolimatech MK-26 Multi-VGA Cooler

ZOTAC GeForce GT 640 ZONE Edition Fanless GPU

SPCR’s 2012 Graphics Card/Cooler Test System

ASUS GeForce GTX 680 DirectCU II OC

Sapphire HD 7750 Ultimate Edition

Arctic Cooling Accelero Xtreme Plus GPU Cooler

* * *

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