Today's Hard|Forum Post
Today's Hard|Forum Post

Quad-GPU Performance Review NVIDIA vs. AMD

How does NVIDIA's GeForce GTX 590 SLI Quad-GPU compare to AMD's Radeon HD 6990 CrossFireX Quad-GPU? We will find out if these "if-money-didn't-matter dream video card setups" will deliver the gameplay experience we all expect.


Wanting to achieve the best gameplay experience possible is a worthy goal for hardware enthusiasts that play video games. Enthusiasts try to obtain this by taking what they have and pushing the hardware to its limits in order to squeeze out every bit of performance the hardware is capable of. For gamers on a budget, or those looking for the best value, or bang for the buck, these type of tweaks provide performance improvements resulting in a better gaming experience for "free."

What if money wasn't a concern? What if you wanted to plop down all the cash that is required to own the best possible performing video card configuration for gaming with no tweaking? There would only be two options right now that would give you the best possible performance, and that is a Quad-GPU configuration from NVIDIA or AMD. While most gamers enjoy performance with one GPU, sometimes it just isn't enough. NVIDIA's and AMD's solution to this problem is to throw more GPUs at you and hope it does what you need.

GeForce GTX 590 SLI

From NVIDIA, you can enjoy dual-GPU on a card from the new GeForce GTX 590. The GeForce GTX 590 utilizes two GTX 580 ASICs (i.e. the actual GPU of a GTX 580 x2), however, the clock speeds are severally reduced as well as the memory speed. This reduction in frequencies has resulted in subpar performance in our evaluation. We found that the GeForce GTX 590 seemed to perform about the same as GeForce GTX 570 SLI. This wasn't entirely exciting considering the high price of $699 MSRP. However, there may be some redemption in the GeForce GTX 590 because it supports Quad-SLI. That is, you can put two GeForce GTX 590 cards in your system and connect those via an SLI bridge for Quad-SLI, or as we will call it, GeForce GTX 590 SLI (two cards with SLI enabled that contains 4 GPUs total.)

The one concern we have is that each GPU only has 1.5GB of RAM to work with. The memory is not shared in SLI using Alternate Frame Rendering (AFR), and therefore each GPU needs its own framebuffer space, and each only has access to 1.5GB. This has the potential to severely limit the performance of GTX 590 SLI, but we will see.

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We are using two ASUS branded GeForce GTX 590 video cards provided to us by ASUS specifically so that we could provide this performance evaluation to our readers.

One thing we will say about the GeForce GTX 590 is that it is one sexy video card, if a video card can be sexy. NVIDIA knows how to design visually pleasing hardware. These video cards are slender and fit nicely in our motherboard with room to breathe. Both require 8-pin power connectors, and our power supply only has three so we had to use an 8-pin adapter that gets its power from two 6-pin connectors. Having enough or the right power connections is something to keep in mind if you are considering building Quad-SLI.

Configuring the display panels was a bit tricky using three DVI connections. You have to plug the displays in a certain way in order for NV Surround to work with Quad-SLI. The pattern we have above is what works, you have the right and center display on the top two ports on the primary video card, and the left display on the top port closest to the other video card. Any other configuration did not work, this is how it must be attached, at least in our experience. We have to say this is more complicated than configuring AMD Eyefinity which doesn't care where you plug in the displays. After we plugged everything in properly, the software enabled NV Surround and we were up and running with Quad-SLI enabled.

AMD Radeon HD 6990

On the AMD side, AMD has produced the AMD Radeon HD 6990 video card. This is also a dual-GPU video card, sporting two Radeon HD 6970 GPUs. These GPUs are also reduced in speed from a Radeon HD 6970 GPU, but not as severely as the GTX 590's GPUs are. The Radeon HD 6970 runs at 880MHz, and the GPUs on the Radeon HD 6990 run at 830MHz, a decrease of only 50MHz, versus the large decrease of 165MHz with the GTX 590 vs. GTX 580 GPU. The memory is also not as severely decreased in speed as the GTX 590 is compared to the GTX 580.

This means that each Radeon HD 6990 GPU is closer in performance to its native ASIC performance than the GTX 590 is. Also, AMD provides a BIOS switch atop the video card that lets you easily put the 6990 into full 6970 GPU clock speeds should you wish to overclock the card.

AMD supports Quad-GPU by allowing us to plug in two Radeon HD 6990 video cards and connect those via a CrossFireX link bridge. The Radeon HD 6990 has 2GB of RAM per GPU, 500MB more per GPU than the Quad-SLI configuration. This means that each GPU has more RAM to access in the same Alternate Frame Rendering (AFR) method used in multi-GPU configurations today. This higher memory capacity should theoretically allow us to utilize the performance better and enable higher settings at high resolutions.

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Setting up Radeon HD 6990 CrossFireX was similar to GTX 590 SLI, we installed both video cards, setup the bridge connector and plugged in the power similarly. When it came to the display setup configuration it was much easier than Quad-SLI. It didn't matter what order we plugged the display port connectors in on the primary card, the software did the job of configuring everything. Also a difference is that all three displays can be plugged into the primary display with AMD Eyefinity, whereas with NV Surround you have to plug two displays in the primary card and one display in the secondary card. Personally, I like the setup of AMD Eyefinity better, its easier and quicker to get setup and going with no hassle.

Game Issues

The gameplay evaluation you are going to see today is as simple as it gets, a true 4-GPU vs. 4-GPU showoff to see who delivers the best performance and best gameplay experience and ultimately the best value.

While the setup is simple, our experiences were a mixed bag. We actually encountered a lot of game issues along the way. We've been trying to work through these issues in our testing time, and worked with NVIDIA and AMD to try and resolve these. We have even switched drivers mid-evaluation, to make sure we were up to date with the latest possible fixes. We tried to keep it as simple as we can and we will explain on each game page what we experienced. Quad GPU gameplay does not come without it problems and surely this will make you question the value of either of these solutions.

The three games we had troubles with were F1 2010, Battlefield: Bad Company 2 and Dragon Age II. It wasn't just NVIDIA or AMD that had issues either, both shared some issue with Quad-GPU. While we have tried to test as high as possible at 5760x1200 in a triple-display configuration, some games we had to actually compare at 2560x1600 on a 30" single display because of issues.

Therefore, this evaluation is a mix of testing at triple-display and single-display. We also have apples-to-apples at both resolutions in a lot of the games. We have therefore provided performance in two areas we know gamers want to see, multi-display performance and single-display performance with really fast video cards.