AMD Radeon HD 6790 Review

Author: Chris Ledenican
Editor: Howard Ha
Publish Date: Tuesday, April 5th, 2011
Originally Published on Neoseeker (http://www.neoseeker.com)
Article Link: http://www.neoseeker.com/Articles/Hardware/Reviews/AMD_Radeon_HD_6790/
Copyright Neo Era Media, Inc. - please do not redistribute or use for commercial purposes.

Since the launch of the Northern Islands graphics cards, AMD has filled the market with high-end and mid-range graphics cards that were based on either the Barts or Cayman GPU. AMD also catered to the lower-end market with graphics cards such as the HD 6770 and HD 6750. With the recently released of the Nvidia GeForce GTX 550 Ti, there was a hole in AMD's lineup that needed to be filled. To close all the gaps and ensure they have a high performance graphics card that competes at the $150 price point, AMD is releasing the latest graphics card from the Northern Islands series – the HD 6790.

The HD 6790 uses a variant of the Barts GPU dubbed the "Barts LE". This new core includes 800 Stream processors that are organized in 10 streaming multiprocessor units, which gives the core two blocks of 400 Steam Processors with each block having a dispatch unit. In addition, the reference Barts LE core is clocked at 840MHz and includes 40 Texture units, 16 ROPs and a compute power of 1.34 TFLOPs. This should give it an impressive performance for an entry-level graphics cards, but AMD has also ensured the HD 6790 will not be limited by its memory sub-system by giving the card a 1GB frame buffer with a 256-bit interface.

By increasing the memory bandwidth, the HD 6790 should not only perform better than other similarly priced graphics cards but also scale better at higher resolutions. According to AMD, the sweet spot for this card is really found in resolutions up to 1080p.

The HD 6790 is designed to offer excellent gaming performance at a price that won't break the bank, and for this reason AMD has set the launch MSRP to $149. This places the HD 6790 directly between the HD 6850 and HD 5770, and sets it up to go head to head with the GTX 550 Ti. So, it should be interesting to see which card comes out on top. Both feature strong internal specifications for their market position, and also have a robust memory interface. Along with the Barts LE core and 256-bit memory bus, the HD 6790 also includes full support for AMD’s latest technologies such as Eyefinity and HD3D

Also, a last minute surprise showed up at the Neoseeker labs in the form a Sapphire HD 6790. With less than 12 hours to go before launch it was a race against time to get it into the launch review,  but we managed to do it in time, and we even got ourselves CrossFire numbers to boot!

Visually the reference HD 6790 is identical to its older sibling the HD 6870, as both use same dual-bay heatsink shroud that measures 9.5 inches in length. They also both utilize the same black and red color scheme and include a large blower style fan at the end of the PCB. However, where the two cards differ are the internal specifications of the Barts based graphics processor. Additionally, even though the reference board resembles the HD 6870, AMD's AIB partners are going to be releasing their own custom designs, so its unlikely that the boards on the market will look like our sample.

The HD 6790 uses the new Barts LE GPU, which like is predecessor is built on a 40nm process that packs in 1.7 billion transistors and has a die size of 255 mm². Also since the core is Barts based it uses AMD's VLIW 5 Shader architecture. The GPU comes clocked at 840MHz and includes 800 Stream processors and 96 texture units, giving it a total compute power of 1.34 TFLOPs. In addition, the HD 6790 also includes a 1GB GDDR5 frame buffer that comes clocked at 1050MHz (4.2Gb/sec effective) and runs on a 256-bit interface.With these specifications the HD 6970 is positioned between the HD 5770 and HD 6850 in terms of performance.

The back panel of the HD 6790 is also identical to the HD 6870. From this angle you can see that the HD 6790 includes dual 6-pin power connectors, is equipped with eight memory chips that surround the GPU in a L shape, and that there is only a single CrossFire connection. As with the HD 6870, you can see that the VRM on the HD 6790 is located in front of the GPU, which puts it closer to the exhaust port. This can help reduce the GPU temperature by reducing the hot air that is pushed through the GPU as it is exhausted out of the card.

The HD 6790 includes a single CrossFire connection point, so this card will include 2-way CrossFire support. The nice thing here is that the HD 6790 can be linked with any other Barts based graphics card, so you can essentially CrossFire the HD 6790 with either a HD 6850 or HD 6870 for improved gaming performance. Of course there will be some reduced performance as we are scaling a lower-end card with a higher-end model, but there should still be a boost in performance compared to a single card setup.

The specification that surprised us the most was the HD 6970's TDP of 150W. That is high for an entry-level graphics card, as most graphics cards in this performance range tend to have a TDP under 150W, requiring only a single 6-pin connection for power. The HD 6790, however, has needs dual 75W 6-pin PCIe power connectors and also requires a power supply with a minimum rating of 500W. The idle power rating, however, is quite good as the board only consumes 19W of power at times of low use.

Also, AMD has brought to our attention that their AIB partners will use custom designed PCB, power connectors, cooler designs. The keyword here is power connectors. According to AMD, the power connection configuration is entirely up to the board partners, so there should be models hitting the market that may only use a single 6-pin power connector.

The rear video outputs on the HD 6790 are the same as those found on other Barts and Cayman based graphics cards. These includes a single HDMI 1.4a port, two Mini DisplayPorts, one SingleLink-DVI port, and a DL-DVI port. Like the other cards in the series, the Mini-DisplayPorts use the 1.2 standard, giving them a higher bandwidth and refresh rate, allowing each port to support Stereoscopic 3D, A/V and even multiple displays through a single port. The HDMI port is also updated to support the latest technologies, as the 1.4a connection now adds support for stereophonic 3D with AMD's HD3D Technology.

The Sapphire graphics card we are also looking at in this review shares the same video outputs as the reference model. However, AMD's AIB partners are able to configure their graphics cards output configurations, so there will be various options available at launch.

The thermal solution used to cool the Barts LE core is again the same as the one found on the Barts XT based HD 6870. The reason this cooling solution is used as opposed to the smaller one found on the HD 6850 is due to the higher power requirement of the HD 6790. More power equals more heat, and thus a more robust heatsink is needed to ensure the core remains within its optimal thermal range.

The heatsink consists of a rectangular-shaped fin array that has three copper heatpipes that transfer heat from the core to the fins. Its placed directly in front of the blower fan, which pushes air through the array, where it is then exhausted out of the back of the card. For improved cooling, the heatsink uses a solid copper core that makes direct contact with the GPU. One nice benefit to this design is that all the heat from the graphics card is pushed out of the case, and not circulated throughout it.

The last part of the thermal solution is a metal plate that secures the fan to the PCB, which also serves as a means to cool the eight on-board memory chips and VRM. This is done via thermal pads that are positioned between the metal plate and circuitry on the PCB. This allows the heat to transfer away from the components, ensuring they remain cool.

 

Overclocking the AMD Reference model:

In our labs the Barts LE proved to have a massive overclocking ceiling, as we were able to increase the GPU clock speed by 160Mhz. That's an increase of 19% over the reference clock speed, which gave our model a total clock frequency of 1000MHz. This should greatly increase the overall gaming performance and yield high frame rates across the board. The memory was also able to overclock quite high, and ended up capping out at 1210Mhz (4840MHz effective). To maintain these high clock speeds, we did have to manually adjust the fan speed to a higher RPM, but as you can see the 75% rotation we used was a bit excessive as the GPU was only reaching temperatures of 58°C while benchmarking Unigine 2.1.

 

Overclocking the Sapphire HD 6790:

Like the reference model, the Sapphire graphics card (more details for the card on the following page) had a very impressive overclocking ceiling, but for whatever reason the AMD Control Panel capped the Sapphire model at 950MHz. The Sapphire model easily reached this cap and had some room to spare, but since we were limited by both CCC and time we went with the 950MHz total. The memory on the other hand was capable of exceeding the speeds achieved by the reference card, although it was only by an additional 5Mhz. Still, in all this is a very good overclock and will ultimately increase the total performance in all the benchmarks.

The Sapphire HD 6790 uses the same specifications as the reference model, which gives it a 840Mhz GPU clock speed and a total 1GB frame buffer clocked at 1050MHz (4.2Gb/sec effective) that runs on a 256-bit memory interface. However, where the Sapphire models differs from the reference model is in its custom PCB and fansink design.

The Sapphire HD 6790 uses a dual-slot fansink that has a centrally mounted 92mm intake fan that also has a large heatsink positioned under the fan. In addition, the Sapphire card also uses a sleek black heatsink shroud that has silver accents and a product sticker along the back.

AMD stated their reference design will not be seen on the market, and was merely a sample designed to show the raw gaming power of the HD 6790. Sapphire's model will be a better example of the type of cards we will see upon the release of the HD 6790, with each AIB partner using their own PCB, thermal solution and power connectors.

Under the heatsink shroud you can see the Sapphire model is sporting a rather robust cooling solution for a card in lower mid-range market. On top of this, the HD 6790 also has an additional cooling solution added to the front mounted VRM, which will keep the components cool even during prolong gaming periods. This can help improve the total power efficiently of the graphics card as well as increase its longevity.

On the PCB Sapphire has included eight ELPIDA branded memory chips that surround the Barts LE based graphics processor in an L shape. Additionally, the card uses a 4 + 1 phase unit design, but surprisingly Sapphire has used a iron core chokes are opposed to the ferrite core chokes used in higher-end cards. Still, the rest of the board design is excellent, as it includes all solid Japanese capacitors and has two 6-pin PCIe power connectors.

The thermal solution used on the Sapphire HD 6790 includes three copper heatpipes that extend from the base of the cooler into the aluminum fin array. This will allow the heat to transfer evenly throughout the array, but to improve the cooling even further Sapphire has included a solid copper base that makes direct contact with the GPU. Also, Sapphire has included a large 92mm fan that draws air in from under the graphics card and exhaust it throughout the heatsink. In all this is a very robust design, but since the heat is not directed out of the graphics card, most of the hot air will be dumped back into the case. However, since this is a lower mid-range graphics card we doubt the heat will be great enough to affect the temperature of the other components.

Hardware Configuration:

Drivers:

ATI cards released prior to the 6800 series will be tested using AMD's Catalyst 10.8 drivers, while the 400 series NVIDIA graphics cards will be tested using their 260.89 drivers. All card released after the 6800 series will be used with their release drivers.The GTX 590 was tested with with Nvidia's 297.59 driver.

We are in the process of retesting all of our graphics cards with the latest drivers and should have the results ready within the next few weeks. For AMD we are using their early release of the 11.4 driver, while we are using Nvidia's 270.51 driver for testing.

Benchmarks DX11:

Benchmarks DX10:

Test Settings:

All in game benchmarks were performed at resolutions of 1280x1024, 1680x1050, 1920x1200 and 2560x1600. Vsync is disabled in the control panel, the AA is set to x4 with AF set to x16 and all the in-game settings are turned up to high.

Usage:

Our current power usage testing consists of using Unigine Heaven 2.1 to gauge the power requirement and temperature of the graphics cards. The program applies a very heavy load to the GPU. For the minimum temperature and power consumption the system will be left in an idle state for 15 minutes and for load we will run Unigine in its entirety at the highest settings.

We are changing the way we gauge power consumption and are currently in the process of testing the new method. Instead of using a program designed to stress a GPU to the maximum level, we are going to use the Crysis Warhead benchmark on high settings. We will set the benchmark to run through multiple levels and record the average peak power rating. This will give use real-world results as opposed to just stressing the graphics card to the max. Once we have all of our graphics cards tested using the new method we will update our reviews.

We are also moving our test system over from a open air bench-table to a closed chassis. This will also give us results that are more in line with the average user. As with the power ratings, these results will be ready soon and we will update the reviews to reflect the new readings as soon as they are ready.

 

Comparison Specifications AMD:

 
AMD Radeon HD 6870
AMD Radeon HD 6850
ATI  Radeon
HD 5750
ATI Radeon HD 5770
ATI Radeon HD 5830
ATI Radeon HD 5870
AMD Radeon HD 6950
AMD Radeon HD 6970
Processing Cores
1120
960
720
800
1120
1600
1408 1536
Core Clock
900MHz
775MHz
700MHz
850MHz
800MHz
850MHz
800MHz
880MHz
Memory Clock
1050MHz
1000MHz
1150MHz
1200MHz
1150MHz
1200MHz
1250MHz
1375MHz
Memory Interface
256-bit
256-bit
128-bit
128-bit
256-bit
256-bit
256-bit
256-bit
Memory Type
1GB GDDR5
1GB GDDR5
1GB GDDR5
1GB GDDR5
1GB GDDR5
1GB GDDR5
2GB GDDR5
2GB GDDR5
Fabrication Process
40nm
40nm
40nm
40nm
40nm
40nm
40nm
40nm

 

Comparison Specifications Nvidia:

 
Nvidia GeForce GTS 450
Nvidia Geforce GTX 460 FTW
Nvidia GeForce GTX 470
Nvidia GeForce GTX 480
Nvidia GeForce GTX 560 Ti
Nvidia GeForce GTX 570
Nvidia Geforce GTX 580
Processing Cores
192
336 448 480 384 480 512
Core Clock
783MHz
850MHz
607MHz
700MHz
822MHz
742MHz
782MHz
Memory Clock
900MHz
1000MHz
837MHz
924MHz
1002MHz
950MHz
1002MHz
Memory Interface
128-bit
256-bit
320-bit
384-bit
256-bit
320-bit
384-bit
Memory Type
1GB GDDR5
1GB GDDR5
1.25GB GDDR5
1.5GB GDDR5
1GB GDDR5
1.25GB GDDR5
1.5GB GDDR5
Fabrication Process
40nm
40nm
40nm
40nm
40nm
40nm
40nm

3DMark Vantage is the stunning sequel to 3DMark 06. Futuremark's benchmarking programs have always been at the center of every bragging match. The best way to show that you've got the greatest gaming rig, is to show that you've got the highest 3DMark score. Vantage does just that. It puts your system through a series of strenuous tests, and provides you with a score to brag about!

In our first benchmark the HD 6790 had performance similar to that GTX 550 Ti at the stock level, but it fell slightly behind at the lowest and highest presets. The performance results after we overclocked the core were very impressive, as the HD 6790 positioned itself between the HD 6850 and HD 6870.

Futuremark's latest 3DMark 2011 is designed for testing DirectX 11 hardware running on Windows 7 and Windows Vista the benchmark includes six all new benchmark tests that make extensive use of all the new features in DirectX 11 including tessellation, compute shaders and multi-threading.

In 3DMark Vantage the HD 6790 didn't manage to outperform the HD 6850 even when overclocked, but it was still able to best the GTX 550 Ti at both the stock and overclocked levels.

Unigine Heaven became very popular very fast, because it was one of the first major DirectX 11 benchmarks. It makes great use of tessellation to create a visually stunning...heaven.

Unigine 2.1 is our last synthetic benchmark, and at the moment the score is two to three in favor of the GTX 550 Ti. Next up we will see if these results transfer into our real-wold gaming benchmarks. We are also seeing a rather decent performance increase between the stock and overclocked settings.

Aliens vs Predator is a DX11 Benchmark that runs though a scene straight out of the classic 80’s movie, Aliens. Since it uses DX11, it can often be more than a graphics card can handle.

In our first gaming benchmark the HD 6790 manages to pull ahead of the GTX 550 Ti in all the tested resolutions. Also, this is yet another benchmark where the HD 6790 performs better than the HD 6850 once overclocked.

DiRT 2 is the sequel to Colin McRae: Dirt and it was one of the first games to incorporate DX11 features such as tessellation, accelerated high definition ambient occlusion and Full Floating point high dynamic range lighting. This makes it a perfect game to test the latest DX11 hardware.

At stock levels the HD 6790 managed a stronger showing than the GTX 550 Ti at the highest resolution, but it was slightly behind in the lower three. Once overclocked, the HD 6790 managed to take the lead in all the tested resolutions.

Lost Planet 2 is a sci-fi action-adventure game from CAPCOM that puts players on a fictional planet called E.D.N. III 10 years after the events of the first game. Like the other new games added to our reviews, Lost Planet 2 includes support for DX11 features to enhance the lighting, charters and environments.

Lost Planet 2 really favors Nvidia-based hardware, so its not suprising the HD 6790 fell behind in this benchmark.

Metro 2033 puts you right in the middle of post apocalyptic Moscow, battling Mutants, rivals and radioactive fallout. The game is very graphics intensive and utilizes DX11 technology, making it a good measure of how the latest generation of graphics cards performs under the latest standard.

Metro 2033 is in many ways the DX11 Crysis of its day. It can be hard even for high-end graphics cards to achieve a high frame rate in this benchmark, so overall the performance of the HD 6790 was quite good. Here too the HD 6790 performs better than the GTX 550 Ti. This is made more impressive by the fact that the MSI card we used for testing was overclocked to 950MHz, whereas the stock HD 6790 is still clocked at 840Mhz. In other words, it is outperforming the competition in most games even with a 110MHz slower GPU clock.

Total War: Shogun 2 is a game that creates a unique gameplay experience by combining both real-time and turn-based strategies. The game is set in 16th-century feudal Japan and gives the player control of a warlord battling various rival factions. Total War: Shogun 2 is the first in the series to feature DX11 technologies to enhance the look of the game, but with massive on-screen battles it can stress even highest-end graphics cards.

In Total War: Shogun 2, the HD 6790 performed well at resolutions up to 1920x1200, but it really started to struggle at the higher resolutions. The overclocked settings couldn't save the HD 6790 above 1920x1200, but with the faster speeds it did manage to perform better than the HD 6870.

F1 2010 is a video game based on the 2010 season of the Formula One world championship and is a mutliplatform port. It was developed by Codemasters and released released in September 2010 for the PC, PS3 and Xbox 360, with the PC version including DX11 features.

The results in F1 speak for themselves. At the stock level the HD 6790 performed better than the highly overclocked GTX 460 FTW and once the HD 6790 itself was overclocked, it even managed to jump ahead of the HD 6850.

Batman Arkham Asylum mixes extraordinary visuals with great gameplay, in order to make an excellent benchmark. It's not a stressful as Crysis, but it can still push cards to their limits.

In Batman Arkham Asylum the HD 6790 got thoroughly trounced, as it performed just slightly above the GTS 450.

Crysis Warhead is one of the most graphically intensive games on the mainstream market. It's graphically breathtaking, and can bring any system crashing to it's knees.

Again the HD 6790 outperforms the GTX 550 Ti, and in our testing it actually achieved a very respectable frame rate up to 1680x1050. Overclocking did improve the frame rate a bit, which a allowed it to outperform the GTX 460 FTW at the highest resolution.

Just Cause 2 places you in Panau, Southeast Asia as Agent Rico Rodriguez. The game is a third-person shooter that pits you against countless enemies with the opportunity for plenty of environment destruction. With explosions and gun fire galore, this game is perfect for testing out the latest hardware.

In our last benchmark the HD 6790 takes home the gold, as it manages to perform better than the GTX 550 Ti in all but the lowest resolution.

Temperature:

To measure core GPU temperature, MSI's Kombustor was used. The idle temperature was taken after leaving nothing running for up to 15 minutes. The load temperature was taken 15 minutes after starting Kombuster for Multi-Core graphics cards

The temperature ratings of the HD 6790 are actually very good, as even during load the core ran cooler than that of Nvidia's GTS 450. Since the GPU was able to remain below 70°C during our testing, the fan was able to operate at a lower RPM, which helped reduce the overall acoustics of the card.

Power Usage:

To measure power usage, a Kill A Watt P4400 power meter was used. Note that the above numbers represent the power drain for the entire benchmarking system, not just the video cards themselves. For the 'idle' readings we measured the power drain from the desktop, with no applications running; for the 'load' situation, we took the sustained peak power drain readings at the end of a 15 minute run of Unigine 2.1.

One aspect of the HD 6790 that we were worried about was the 150W TDP, but duing our testing we found that the overall power usage was quite acceptable.

 

Conclusion:

The HD 6790 is designed for gamers looking for a high performance, low cost solution to play the latest DX11 titles and in many ways it is really an ideal solution for its price point. At $149 the HD 6790 offers users good performance in resolutions up to 1920x1200, and can even do so with relatively high settings. In our testing, the stock HD 6790 was able to perform better than the GTX 550 Ti in most of our in-game benchmarks, and once overclocked it was able to compete with more expensive cards, including the HD 6850. In addition, the HD 6790 scaled incredibly well together in CrossFire. This allowed the dual HD 6790 graphics cards to compete with high-end models such as the HD 6970 and GTX 570 in games that scale well with CrossFire.

The performance of the HD 6790 is in large part due to AMD increasing the memory bandwidth beyond what is usually found on graphics cards in this price range. In today’s graphics market it is standard for a $149 graphics card to have a 128-bit memory bus. Nvidia shook up the rules with the release of the GTX 550 Ti by using a 192-bit bus, but AMD has taken it even further and decided to use a full 256-bit memory interface. This reduces memory bandwidth limitations and allows the graphics card to perform better at higher settings and resolutions.

Of course, the HD 6790 is not meant to be used at the 2560x1600 resolution levels and our testing shows this; the performance sharply declined when the settings were above 1920x1200. However, most gamers for now use displays at or below 1080p, so AMD has hit the sweet spot in terms of price to performance.

The only issue we have with the HD 6790 is that it requires dual 6-pin power connectors and that could be a high power requirement for some gamers in this price segment. This due to many budget gamers (including some I personally know) having an inadequate power supply that doesn’t include dual 6-pin power connectors. For this reason we really would have liked to see this card have a lower TDP and needing only a single power connector. However, when testing the total power consumption we were surprised that the peak power rating was less than that of the GTX 550 Ti, which has only one 6-pin connector. So, while it has a high TDP, its total power consumption was still reasonable. Also, some of AMD's AIB partners, such as PowerColor are using boards that include a single power connector.

With the HD 6790 being positioned at $149, it is coming at the same retail price as the GTX 550 Ti and as stated in that review this is a market segment that is currently in a hyper-competitive state. Here graphics cards such as the HD 6850, HD 5770, GTX 550 Ti and others differ in price by as little as $20 in some instances. This is actually very good for the consumer, as both AMD and Nvidia are offering high performance graphics cards for a low premium.

In all the HD 6790 offers gamers great performance up to 1920x1200 and also supports technologies such as HD3D, Eyefinity and DX11. This makes the HD 6790 a good option for anyone looking for great performance without breaking the bank.

»Neoseeker.com

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