AMD Radeon 6990+6970 CrossFireX / "TriFire" Review

What happens when you take an AMD Radeon HD 6990 and add a Radeon HD 6970 to it for 3-way GPU CrossFireX performance? We compare this configuration directly to GeForce GTX 580 SLI a multi-monitor setup at high resolutions. TriFire in all its Eyefinity glory! Along with one new DX11 game.

Introduction

The evaluation we have for you today was born out of necessity due to current online prices on multi-GPU video cards. We initially planned to have this evaluation out much sooner, quickly following the launch of AMD's Radeon HD 6990. However, fate had something else in store for us to work on with the launch of the competing NVIDIA GeForce GTX 590 dual-GPU video card on its heels. Now that these launches are behind us, we have moved on to some interesting comparisons regarding multi-GPU performance. We are going to look back at the Radeon HD 6990 and use it in an interesting CrossFireX configuration that is supported by AMD commonly referred to in the enthusiast community as "TriFire."

In our launch evaluation we tried to cover as many combinations and comparisons as we could in the time we had. We compared the Radeon HD 6990 with Radeon HD 6970 CrossFireX and GeForce GTX 580 SLI. Later, we performed a follow-up evaluation which looked at performance compared to single GTX 580 as well. Our results of the evaluations proved that GeForce GTX 580 SLI still held the crown in terms of ultimate gameplay experience at triple-display resolutions. The Radeon HD 6990 did come close at times, but more often than not the GTX 580 SLI combo simply offered the best experience in the end. Given the GTX 580 SLI price premium, one would hope this would have been the case.

Today a single GeForce GTX 580 will still cost you $500 before $40 MIR! When you put two of these together to enjoy the performance benefits of SLI, and that is going to set you back around $1,000 before MIR. The dual-GPU Radeon HD 6990 will set you back $709 currently. This leaves a rather large $300 gap, and you can see that truly the Radeon HD 6990 is not the competition for GeForce GTX 580 SLI no matter what rebate is given. What does compare to GTX 580 SLI?

Triple-GPU / TriFire is the Answer

It became clear to us early in our Radeon HD 6990 testing that the proper comparison to GTX 580 SLI, due to this pricing, is actually a triple-GPU setup from AMD. AMD supports dual, triple, and quad-GPU CrossFireX in various combinations. The only requirement is that the GPUs are of the same generation and same class. Brand doesn't matter, and clock speed differences don't matter. This allows us to setup a $700 Radeon HD 6990 with a $315 Radeon HD 6970 for triple-GPU CrossFireX performance commonly referred to a "TriFire."

Remember, each GPU on the Radeon HD 6990 is a Radeon HD 6970 GPU. There is also 2GB of RAM per GPU, just like a Radeon HD 6970 video card. The differences lie in the clock speeds. Both GPUs on the Radeon HD 6990 run at 830MHz in the default BIOS position, while a Radeon HD 6970 video card runs at 880MHz. Also, the memory on the Radeon HD 6990 video card runs at 5GHz, while a Radeon HD 6970 runs at 5.5GHz.

Therefore, what happens is the triple-GPU setup will only run as fast as the slowest system. Meaning that though the Radeon HD 6970 video card can run at 880MHz/5.5GHz, it will synchronize with the slower 830MHz/5GHz clock speeds of the Radeon HD 6990. You still have all the goodies, 2GB of RAM, same shader count, but just slightly reduced clock speeds on that video card. Still, we have a lot of processing power.

Setting It all Up

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Setting up this $1,015 configuration matching the $1,000 GTX 580 SLI configuration, is quite easy. CrossFireX used to be a pain in the butt, but AMD has got its act together on this technology now. It is as easy as putting the Radeon HD 6990 in the main PCIe slot, and then putting the Radeon HD 6970 in the next proper slot for CrossFireX. You do have to attach the bridge atop the video card, but only one is needed (as there is only one CrossFireX connector on the Radeon HD 6990 anyway.) You then have to connect all the power connectors, and for this setup there are a lot of power connectors. You will need 3x 8-pin power connectors and one 6-pin. Once you have the hardware installed just boot up and install software.

For our testing today, we are using the latest Catalyst 11.4 Preview driver dated 3/29/2011. We are also using a brand new Catalyst Application Profile that will be released this week, it is Catalyst 11.3 CAP2, which is superior to the Catalyst 11.3 CAP1 currently on the website. Once you install the driver and reboot Catalyst Control Center will automatically enable CrossFireX. You must make sure there is a check mark in that box so that CrossFireX will be enabled between the two video cards. After installing the CAP, that is all there is to it, you now have a 3-GPU CrossFireX setup.

Comparison

For our evaluation today we are going to directly compare these price comparable multi-GPU configurations. Before you start writing us angry emails that we aren't comparing things fairly because one is a 3-GPU setup and the other is a 2-GPU setup, we remind you about price, it is all about what is comparable at the "same' price point. The fact is 3-GPUs from AMD are price competitive with 2-GPUs from NVIDIA right now. A 6990+6970 or 3x 6970's are at GTX 580 SLI pricing.

We will compare the Radeon HD 6990+6970 CrossFireX setup at $1,015 to the GeForce GTX 580 SLI setup at $1,000. Depending on rebates offered there can be as close as a $80 difference between these setups (as of this morning as rebates have increased). So as you read, ask yourself if spending the extra $80 one way or another is worth it at these price points.