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AMD Radeon HD 6990 4GB Review

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SKYMTL

HardwareCanuck Review Editor
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Temperature Analysis & Acoustics / Power Consumption

Temperature Analysis & Acoustics


For all temperature testing, the cards were placed on an open test bench with a single 120mm 1200RPM fan placed ~8” away from the heatsink. The ambient temperature was kept at a constant 22°C (+/- 0.5°C). If the ambient temperatures rose above 23°C at any time throughout the test, all benchmarking was stopped. For this test we use the 3DMark Batch Size test at it highest triangle count with 4xAA and 16xAF enabled and looped it for one hour to determine the peak load temperature as measured by GPU-Z.

For Idle tests, we let the system idle at the Windows 7 desktop for 15 minutes and recorded the peak temperature.


HD6990-73.jpg

With an all new heatsink design and high end thermal compound, the HD 6990 is able to keep both cores very cool for a dual chip card.

Noise does factor into the equation though and it’s not only from the fan. The high end Volterra VRMs are known for their efficiency but are also legendary for the loud hissing / whining they make when under high loads. Other areas of the PWM also contribute which actually makes the components louder than the fan at times. We found that enabling V-Sync reduced this noise but let’s be honest; you don’t buy an ultra high end card to play at a constant 60 FPS.

Meanwhile, the fan itself does make this card noisier than many single card setups but at subjectively equal acoustic levels to most high end dual card configurations. In our experience, the HD 6990’s fan noise is no louder than two HD 6970 cards in Crossfire but that doesn't mean it's anywhere near quiet either.

Aside from the racket the PWM on our card made, there was one other issue: the direction some of the heat travels.

HD6990-15.jpg

When installed into a standard ATX case or even a unique product like the Silverston Raven series, the HD 6990 will be constantly pushing part of its hot exhaust air against the airflow direction of the enclosure. Considering we were seeing temperatures of nearly 130 degrees Fahrenheit, in-case temperatures could definitely be raised.

On the other hand, we actually prefer this design since it keep both cores’ heat well under control and most modern enclosures which are designed to handle this huge card should have no issue dispersing its heat.


System Power Consumption


For this test we hooked up our power supply to a UPM power meter that will log the power consumption of the whole system twice every second. In order to stress the GPU as much as possible we once again use the Batch Render test in 3DMark06 and let it run for 30 minutes to determine the peak power consumption while letting the card sit at a stable Windows desktop for 30 minutes to determine the peak idle power consumption. We have also included several other tests as well.

Please note that after extensive testing, we have found that simply plugging in a power meter to a wall outlet or UPS will NOT give you accurate power consumption numbers due to slight changes in the input voltage. Thus we use a Tripp-Lite 1800W line conditioner between the 120V outlet and the power meter.

HD6990-72.jpg

The HD 6990’s power consumption is as expected very high for a single card but it was actually quite low considering the performance it brings to the table. By specifically binning the cores for the lowest leakage possible and then ensuring they stayed well under the temperature of the HD 6970, AMD ensured efficiency was about equal to that of two HD 6950 cards.

In the chart above we can see the effect higher temperatures, additional voltage, increased clock speeds and higher leakage cores have on the HD 6970 Crossfire solution.

Choosing a power supply for this card won’t be an inexpensive endeavor either. If you plan on keeping it at stock speeds, we are going to recommend a good 850W unit with a single or two large rails to ensure proper delivery. Overclocking brings in a whole new scenario and while this will be discussed in a later section, a good 1000W PSU plus an enthusiast motherboard with a separate Molex of FDD power connector for the PCI-E slots is recommended.
 
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SKYMTL

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Overclocking Results, Performance & Efficiency

Overclocking Results


In their marketing documents, AMD states that the HD 6990 is geared towards enthusiasts since it offers a wealth of overclocking options. Through the use of the dual BIOS switch on the card (otherwise known as the hopelessly named Antilles Unlocking Switch for Uber Mode), enthusiasts can change between a default profile and a more aggressive setup which pushes additional voltage towards the core and ups the GPU’s clock to 880Mhz.

We used both positions in our overclocking along with boosting PowerTune’s overhead to +20% but all in all, the results were a bit mixed since the core did overclock reasonably well but the memory on our card seemed to be held back. Also remember that a “stable” overclock for us means the ability to complete a 1 hour loop of Unigine: Heaven without any artifacts or crashes..

Default BIOS Overclocking (Position 2)

Max Stable Core Clock: 870Mhz
Max Stable Memory Clock: 5444Mhz


“Performance” Profile Overclocking (Position 1)

Max Stable Core Clock: 972Mhz
Max Stable Memory Clock: 5444Mhz


Touching Upon Overclocked Performance


HD6990-83.jpg


HD6990-84.jpg

There are two things to be learned from these results: pushing clock speeds on the HD 6990 can pay dividends but using the BIOS switch is absolutely pointless if you aren’t planning to overclock.

At 972Mhz, the cores are able to work in tandem to spit out some downright incredible framerates and yet there is a heavy price to pay…


Power Consumption


HD6990-85.jpg

The words “mind blowing” come to mind when looking at these results. With the BIOS switch in Position 1 and additional voltage coursing through the cores, we can definitely see where the 450W claim comes from. In addition, just moving the switch without actively increasing the clocks past 880Mhz still results in much higher power requirements since the cores are being fed with higher voltages.

With all of this in mind, several questions must be raised before proceeding to overclock this card. More overclocking will cause massive amounts power to be pulled from the PCI-E slot so buying a motherboard with an optional GPU Molex or FDD power connector would be a good idea. This will feed more +12V power to the GPU.

In addition, anything more than 400W of draw could spell trouble for some multi rail power supplies with 18A rails. For these cases, we recommend that you be very careful with which connectors are used for the HD 6990.
 
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SKYMTL

HardwareCanuck Review Editor
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Conclusion

Conclusion


Going into this review, I was perfectly happy to set myself up for disappointment since dual GPU cards have almost always fell short of expectations. Whether it was driver issues, excess noise or something else, there has usually been some major pothole preventing me from buying what products like the GTX 295, HD 4870X2 and HD 5970 were trying to sell. AMD’s HD 6990 on the other hand has proven that my apprehension was misplaced as it threaded its way perfectly between the two other top-end Crossfire solutions.

What we have with Antilles is an experience which is which is quite a bit different from the ones its predecessors put forth. Instead of shaky game support, a Dust Buster-like acoustical profile and rampant core heat, the HD 6990 currently has a good driver foundation which backstops some truly impressive performance results. The GPUs themselves are kept relatively cool by way of an innovative cooling system that is no louder than a pair of HD 6950 cards. Unfortunately, the voltage regulator hiss is annoying and can usually be heard above any noise the fan makes...and the fan isn't what you would call quiet.

Power consumption numbers may seem stratospheric for a single card but that’s the price one has to pay for class-leading framerates. With that being said, if put into context against competing dual card setups, AMD’s choice to pick low leakage cores coupled with relatively low temperatures tends to keep overall power needs at a lower point than many would have expected.

HD6990-82.jpg

If rumors are to be believed and NVIDIA is well on their way towards designing a competitor to Antilles, things could get very interesting indeed. Judging from our results, AMD’s new card holds its own against GTX 570s in SLI which makes perfect sense consider its price lines up perfectly against the competition’s dual cards. Things do turn around at 5760 x 1080 resolution with AA enabled where the GTX 570’s framebuffer proves to be insufficient and the HD 6990 can pull ahead. Against the ultra expensive dual GTX 580s, Antilles is simply overpowered at every turn but that was to be expected considering the $1000 price of NVIDIA’s high end setup.

As with every other multi core graphics cards, the success or failure of the HD 6990 largely hinges on AMD’s driver development team stepping up to the plate in a big way. As we saw in testing, its mission accomplished….for now. If they can keep this head of steam going and roll out application profiles in rapid order as the busy spring gaming season heats up, then early adopters should have nothing to fear. However, if Crossfire support for new games trickles out months after release, Antilles’ design could be rendered ineffective in short order. It should also be mentioned that while driver stability was spot-on, the Catalyst Control Center is another matter altogether and if you’re upgrading from a previous AMD card, be ready to face some possible issues.

True success in the graphics card market is hard to come by but AMD seems to have found the right formula for Antilles. Even though pricing alone will likely keep most people away, it has forced me to rethink my preconceptions about dual core products. As such, it really does deserve consideration for those of you looking for best money can currently buy.

There are sure to be challenges for the HD 6990 in the future but if initial indications are anything to go by, AMD is ready and willing to ensure that it succeeds.




 
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