Radeon HD 6990 Review
It's always a sign of great confidence when a dual GPU card is released. ATI did this last month with their Radeon HD6990 which we are reviewing today and shortly after this, Nvidia launched their GTX590. The former houses two HD6970 cores and the latter two GTX580 cores. We have been unable to obtain a GTX590 to review (they are incredibly scarce) so lets start this review by answering a key burning question based on results from other sites - the ATI Radeon HD6990 is faster than the Nvidia GTX590! The reasons for this are due to power constraints and we'll show exactly why during the course of this article. Now we have got that out of the way, we can explore the HD6990 in depth and compare performance with a number of high and mid-range cards.
Since the 5970 was launched last year it has become clear that thermal dissipation is the key limiting factor for any graphics card. The 5970 has two 5870 cores but runs 125MHz slower (200 MHz slower for the RAM) than a single 5870. The 6990 is only 50MHz slower than a 6970 in core speed but a massive 500MHz slower in RAM speed. Even so, the 6990 is rated at a massive 375W TDP which is right at the limits of what a PCI-E slot (75W) and dual 8-pin connectors (150W each) can provide. Furthermore, automated regulatory circuits on the card will throttle back the speed to stay within this thermal envelope and this happens on some benchmarks (most notably FurMark which is currently the most strenous GPU test available).
This compromise would be grudgingly accepted by consumers but AMD/ATI have gone much further to satisfy their consumers by including a (not so) secret switch on the card which "overclocks" the card to the full specifications of 6970 speed, i.e. 50MHz faster core and 500MHz faster memory. Doing so disables the thermal protection circuits and the limits go out the window. TDP can shoot up to extreme levels as we will see later. Needless to say, this is done at the risk of the consumer and removing the security sticker over the button invalidates the warranty but is the only way to achieve true CrossFire performance with a single card.
Here are the specifications of this card:
Initial price is higher than for the HD5970 (now discontinued) and at double that of a 6970 is competitive with performance (particularly if switched to full performance mode). Having said that, here in the UK (despite a massive 20% sales tax), we have seen the 6990 on sale for as low as £499 and expect lower prices in coming weeks and months if supply is sufficient. This is the opposite of what happened with the 5970 which was only available at above its $599 price point due to high demand and short supply. There is plenty of stock available at present (unlike the Nvidia GTX590) so this is most definitely not a paper launch.
Architecture remains the same as the 6970 and at 40nm:
The highest-end Cayman configuration offers fewer ALUs than the most complex Cypress processor (found in the Radeon HD 5800-series cards). However, Caymanís ALUs are more flexible.
This is how different types of CODEC are handled with the greatest degree of hardware assistance going to the more complex ones. Even HD Mpeg-2 can be handled by a simple CPU but 3D Blu-Ray can certainly do with this type of offloading.
Moving on to the card itself we see that it is quite a beast.
Unlike the 5970 we can see that the cooler is placed in the middle so air is blown equally in either direction. The end placement on the 5970 meant that one of the GPUs got better cooling than the other and also that VRMs overloaded quicker than the GPUs. This redesign coupled with special phase change thermal material gives what AMD claim is the best thermal dissipation available anywhere short of liquid cooling. The main drawback of this design is that hot air is now also vented into the case as well as out the back. As we'll see later, this can have a significant impact on air temperature inside the case.
The back of the PCB shows the location of the GPUs and part of the yellow security sticker.
The two side views show the boxiness of the reference design (this is unlikely to change as manufacturers will use this because of the special thermal materials employed so visible changes will likely just be cosmetic). The two 8-pin connectors are placed on the side of this already long card.
The 8-pin connector sockets are solidly mounted (good thing as they carry 150W each as standard and much more at "full" speed). AMD have designed the card to take extra power in overclocked mode from the 8-pin connectors rather than the PCI-E slot. This will prevent damage to the motherboard but users will need to carefully spec their power supply to ensure it can handle extreme power draws. We used an Antec 750W PSU during our testing and had no problems at the maximum system draw of 614W. Be advised that PSUs start to suffer their greatest strain when running above 80% of their rated capacity. Their fans spin faster and the components run hotter - something which may significantly reduce the lifespan of the PSU.
The yellow sticker is a bit of a dilemma for consumers. Should they invalidate their warranty and get the best perofrmance or is the stock performance good enough? Fortunately we ran our tests with the switch in both positions so our readers can see for themselves if it is worth doing.
The inside edge of the card is open due to the centrally mounted cooler so that the heat from one of the GPUs goes straight into the case.
The back shows lots of mini DPs (retail cards will come with an HDMI adaptor) and a single DVI port. 5 monitor support is available straight out of the box but a hub will be needed for full 6-monitor eyefinity use. The exhaust grill is a full slot in width and really needs to be this big.
In case we hadn't stressed it enough, the above picture shows that the 6990 is a full 12 inches in length. While its thankfull that the power connectors are on the side, most cases will have trouble getting the card in comfortably. Our Antec 902 required the removal of some drive bays before we could fit the card inside. It's a good idea to do some proper measuring before ordering this card or, if ordering a new case too, getting some assurances of compatibility.
We have two main test systems at present and recently upgraded our Intel one to an i7-2600K we received from Intel for the Sandy Bridge launch in January. The AMD system has the most powerful processor currently available in the AMD range. All cards are tested at their default speed but in the case of the Radeon HD6990 we are able to get it to run at full 2x 6970 speeds by flicking a switch on the card. Therefore we will show results as HD6990 and HD6990 OC to distinguish between them.
Memory is shown as 4GB but because of the dual GPU design this is 2GB per card (textures etc are duplicated per card). On the left is the stock speed and on the right is the card running at "full" speed. This will be listed in all forthcoming graphs as 6990 OC.
Firstly we will start with DX10 testing (the range of DX11 games is still limited at present although we benchmark two of them in the next section.
3DMark Vantage is a full DirectX 10 compliant synthetic benchmark. It tests out all of the DirectX 10 abilities of each card to give the user an idea of where they rank with their graphic card in a collective pool of many users all over the internet.
Futuremarkís 3DMark 11 is a synthetic benchmarking tool designed to provide an accurate and consistent simulation of the latest DX 11 games. 3DMark 11 tests the video cardís performance capabilities using a native DirectX 11 engine which uses tessellation, compute-shaders and multi-threading. 3DMark 11 also tests the systemís physics capabilities using the Bullet Open-source physics engine, testing for rigid-body calculations via CPU, as well as simulating soft-body physics using DirectCompute.
The testing was done with the default performance setting for all of the cards to give an idea where each one stands in the GPU line up.
The closest single card competitor is the Nvidia GTX580 which only manages about two-thirds of the graphical performance. The Radeon HD5850 (approximately the performance of a 6870) falls significantly behind. Physics scores are similar for all cards because the test rig (and hence the CPU) is the same.
Setting aside the middle bars (the CPU performance is fairly level as the only variable during testing is the graphics card) it can be seen that the performance of the high end cards scales with their product positioning. The Radeon HD 5850 which has served us so well for over a year is still capable of putting up a good fight but is now end of line and is about the same price as the better performing Radeon HD 6870. The Sapphire Radeon HD 6950, currently priced about 20% higher than the two others shows a nice boost in performance and we'll see how that translates into real-world benchmarks. Both the GTX580 and the HD6990 manage to reach around the 30000 mark which is no easy thing. The performance boost of running the 6990 at full speed is actually quite low.
Far Cry 2 is a sequel to the original Far Cry. The game features an open-ended experience. Players are able to ally with one or multiple factions, and to progress through the game world and missions as they see fit, resulting in a nonlinear style of gameplay commonly referred to as sandbox mode that allows the story to progress at their speed and in the order they choose. Players can utilize a range of vehicles, including cars, trucks, boats and hang gliders, to travel within the 50 km2 (19.3 sq miles) gameplay area. The playing styles range from head-on assaults to stealthy infiltrations and assassinations. The game takes place in a sprawling African landscape, with terrain ranging from desert to savannah to jungle.
Far Cry 2 is still a firm favourite and was taxing on any system. It's now broken by the HD6990 and is CPU limited at all resolutions! Considering that our i7-2600K Sandy Bridge processor is the most advanced available, that is quite an achievement. This is unexpected and requires careful analysis. On the other hand the GTX580 performs well all the way up to full HD resolution.
The simplest explanation is that the quad core i7-2600K cannot keep up with the 6990. It will be interesting to see how things change when we get our hands on an 8-core Bulldozer CPU.
Taking off from a long line of successful first-person shooters, H.A.W.X is the first flight combat game from the Tom Clancy interactive entertainment franchise. While realistic presentation in the game's graphics, audio, and speculative fiction plotline are central to the experience, the play of the game is available at two main levels of realism. By default, a built-in "Enhanced Reality System" serves as a sort of automated co-pilot, providing damage control, targeting, missile detection, squadron management, assistance with stabilization and handling of the aircraft, and similar functions. With the touch of a button, some or all of these auto-assist systems can be disabled, giving the player much more maneuverability and providing a more demanding, simulation-style experience.
HAWX seems to be easy for most systems to handle with playable rates from all contendors at all resolutions. We'll have to see how that changes when we move to HAWX 2. The Radeon HD6990 is a clear leader at all resolutions although there seems to be no benefit to running the 6990 in "full" mode.
The current darling of horror games provides lots of eye candy and furious action. As with Far Cry 2 performance is very good but only the 6XXX series cards can provide triple digit frame rates at all resolutions. The ASUS ENGTX580 is just as fast as the more expensive HD6990 except at the highest resolutions. Once again, we see no benefit to pushing the 6990 beyond its default capabilities.
We're in the process of changing our benchmarks to more demanding ones and appreciate any feedback suggestions.
We cannot give exact decibel levels due to lack of sufficiently sensitive equipment but can confirm that the ATI Radeon HD6990 is fairly quiet most of the time but noticably loud under strain and under extreme cases (such as FurMark) sounds like a dustbuster!
Power consumption is a big issue these days with GPUs sometimes consuming 2 or 3 times as much as a CPU. Performance returns never seem to scale anything like power increases and heavy users can find that the cost of increased electricity mounts up over time. The idle loads shown are all perfectly acceptable but under load (running Resident Evil 5 fixed benchmark) the HD6990 jumps to around 400W while the GTX580 is closer to 300W. Using FurMark the HD6990 overclocked (cores running at full HD6970 speed) uses 614W of power versus 485W at normal setting. That's a 130W increase for about a 7% increase in clock speed.
Temperatures determine how long a component will last and can affect other components in a case. The HD6990/HD6990OC temperatures are 44/48 idle and 86/93 in FurMark despite an extremely well ventilated case. This is high and one questions whether running 7 degrees hotter and thereby shortening component life can be justified by the limited increased performance.
Because of the longevity of our standard tests we have introduced Alien vs Predator and Stalker: Call Of Pripyat as two new benchmarks. We wanted to add Crysis2 as well but DX11 issues with that title mean we will have to wait until a patch is released. The performance of Dragon Age 2 is flaky under DX11 and that too will have to wait for a patch.
Aliens VS Predator
As with many of the already released DirectX 11 benchmarks, the Aliens vs. Predator DirectX 11 benchmark leverages DirectX 11 hardware to provide an immersive game play experience through the use of DirectX 11 Tessellation and DirectX 11 Advanced Shadow features. In Aliens vs. Predator, DirectX 11 Geometry Tessellation is applied in an effective manner to enhance and more accurately depict HR Gigerís famous Alien design. Through the use of a variety of adaptive schemes, applying tessellation when and where it is necessary, the perfect blend of performance and visual fidelity is achieved with at most a 4% change in performance.
The 6990 leaves all competitors far behind, even managing triple digits at full HD resolution..
Stalker: Call of Pripyat
This is a special version of S.T.A.L.K.E.R.: Call of Pripyat Having a PC tested with this benchmark will enable the gathering of detailed information about its performance on various graphical modes and finds out how well the system is balanced for gaming and S.T.A.L.K.E.R.: Call of Pripyat in particular.
This benchmark is based on one of the ingame locations Ė Pripyat . The testing process includes four stages, those utilizing various weather and time of the day settings (day, night, rain, bright sun). In order to test the system thoroughly the benchmark is provided with a number of presets and options including different versions of DirectX (9.0, 10.0, 11), screen resolutions, antialiasing etc.
We use the Ultra (highest details) setting and DX11 mode. The only switching we did was between 1680x1050 and 1920x1080 resolutions and to switch the DX11 Hardware Tesselation and Contact Hardening Shadows.
While the HD6990 is a clear winner at maximum frame rates, the GTX580 is just as good at average frame rates and often has much higher minimum frame rates. This translates into a smoother performance than its more expensive rival.
Performance hit for going up to 1920x1080 is negligible for all except the Radeon HD5850.
Enabling HW Tesselation and Contact Hardening Shadows provides a huge boost in visual quality. This alone is worth the small performance hit (good programming from the developers - compare that with the hit from doing the same in Dragon Age 2).
Now with everything maxed out (we need a better test monitor to achieve 2560x1600) we are still getting perfectly playable (usually over 100fps) average frame rates from the ASUS ENGTX580 DCU2 but the maximum rates from the 6990 show that the card is capable of much more.
Having the latest graphics card is not just about speed but also other benefits. One of these is hardware acceleration in video playback and this is illustrated with Adobe's Flash player with support for hardware acceleration.
The difference is startling and shows how important this feature can be if widely implemented. Let's hope that people keep pestering the relevant software developers until they all have this level of support by default.
To see the benefits of DX11 that are unique to the DX11 series cards we need to dig further. Itís tricky to test to see how much of a speed difference DX11 makes as there are few reliable DX11 benchmarks but as a showcase of DX11 quality the situation is much better. We used Unigineís Heaven Benchmark and can only convey the quality to our readers via YouTube.
The improvement in quality is apparent for all to see.
This next video shows the effects of Hardware Tessellation. The technical white paper on this feature is enough to send the most avid technophile to sleep but there's no denying the benefits of the end result.
If you have a DirectX 11 card then you can download the demo for yourself at http://unigine.com/download/
The AMD Radeon HD6990 is clearly once again the Single Card King. Not only is it the fastest card available, it shows glimpses of much greater performance if processors and software would allow it. The first clue was the CPU limitation at all resolutions in Far Cry 2. We got another clue with the stellar maximum frame rates in Stalker:COP that it can handle much more complexity and remain playable.
The switch that removes all restrictions from the card will be welcomed by enthusiasts and shows that the designers have listened to their target consumers since the 5970 release. Performance boosts are minimal from doing so however, and we would recommend preserving the warranty - for now. Common sense tells us that the same limitations mentioned above are hindering the card and with more powerful future CPUs and more complex games, switching to "full" mode will then have a more profund impact.
The card is noisy but that will not deter the target market segment, nor will the price which is similar to buying a pair of 6970s in one single convenient package. A power supply of at least 750W is needed but we recommend 1KW if budgets can stretch that far. Because hot air is vented inside the case, it is even more important than ever to have good airflow.
For the enthusiast the greatest value proposition is this:
"Reasonably priced, the Radeon HD6990 offers the best performance today compared to any card and represents a good future investment as performance will increase even further a year or two down the line with better processors and more innovative use of DX11 in future games."
We believe AMD have managed to get the mixture just right with the Radeon HD6990.
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