GeForce GTX 680 3-Way SLI & Radeon 7970 Tri-Fire Review

What do you get when you install three GeForce GTX 680 cards for 3-Way SLI and then three Radeon HD 7970 cards for Tri-Fire? You get insanely fast gaming performance and a gameplay experience that begs to be compared delivered by both. We find out which multi-display configuration is better for gaming in Eyefinity and NV Surround.

Introduction

We've evaluated the NVIDIA GeForce GTX 680 and AMD Radeon HD 7970 in single-card form; we've evaluated both in dual-card configuration comparing SLI and CrossFireX. Now it is time to take it to the next level and compare the two competing products in triple-card setups. This evaluation takes a look at the gameplay experience between GeForce GTX 680 3-Way SLI (3x GTX 680 cards) and AMD Radeon HD 7970 Tri-Fire CrossFireX (3x HD 7970 cards) for the ultimate test of performance one can get in gaming today.

On paper, the Radeon HD 7970 has two advantages when in combinations of two or three video cards. The first one deals with the VRAM capacity itself. The second issue deals with the memory bandwidth available. On the first note, the Radeon HD 7970 has 3GB of VRAM per video card. As we know, CrossFireX and SLI require that the image be copied across memory, and you don't get a combined VRAM capacity. Therefore, the amount of VRAM on one video card is the maximum VRAM the SLI or CrossFireX configuration has available to it. Therefore, with HD 7970 Tri-Fire you have 3GB of VRAM capacity for textures and everything to work within. With GeForce GTX 3-Way SLI you only have 2GB of VRAM to work within, as each video card has 2GB per GPU.

The second specification Radeon HD 7970 Tri-Fire has going for it is memory bandwidth. Each Radeon HD 7970 video card has a 384-bit bus with memory running at 5.5GHz, which provides 264GB/sec of memory bandwidth. In comparison, each GeForce GTX 680 video card has a 256-bit memory bus with memory running at 6GHz, providing 192GB/sec of memory bandwidth. On paper, HD 7970 Tri-Fire should have advantages when it comes to running three video cards together. In the real-world, it doesn't always work out the way you think it should.

Setting up Radeon HD 7970 Tri-Fire CrossFireX

Setting up Radeon HD 7970 Tri-Fire was a cinch in terms of the hardware installation. We put all three Radeon HD 7970 video cards in our system and properly hooked up the CrossFireX connectors. Two CrossFireX connectors are required in this configuration. You must place the first one between the primary video card and the second video card. Then, you attach another CrossFireX connector between the second video card and the third video card. This completes the Tri-Fire setup. We plugged in our displays all to the primary video card. We had one display on DVI and the other two on DisplayPort. This configuration worked great and we were able to turn on Eyefinity. All three video cards were operating at stock HD 7970 core and memory frequency.

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This is where the "good" ends, and the "bad" begins. There is a major issue with driver support on a configuration with Radeon HD 7970 Tri-Fire + Eyefinity that AMD does know about. It is a known issue by AMD, and a known issue by our readers in our forum. This issue is this, you cannot run with any driver version greater than the 8.921.2 RC11 driver that was initially released back in January of 2012 if you want to run games with Tri-Fire + Eyefinity enabled. If you install any driver, including the latest 12.3 WHQL driver, and enable Tri-Fire and turn on Eyefinity every game will BSOD. Another stellar public performance by AMD’s driver team!

The issue is directly related with Eyefinity in Tri-Fire mode. When you disable Eyefinity, and operate on a single display Tri-Fire works just fine and games run with current drivers. When you enable Eyefinity across more than one display, gaming is now broken with every driver except RC11 driver dated from January.

We asked AMD about this issue and AMD stated that it is known and a fix is in the works. Apparently though, it is not a priority. Thet fix isn't going to come this month with Catalyst 12.4, and in fact, it may be Catalyst 12.5 before we see this fixed. Therefore, the only way to run Tri-Fire + Eyefinity is to use the 8.921.2 RC11 driver. You can however download and install the latest Catalyst Application Profile. We downloaded and installed 12.3 CAP1 and it worked just fine, so at least you'll have the latest CrossFireX profile support in games, you just have to run with a 4 month old driver. We'll talk more about this in the conclusion.

Setting up GeForce GTX 3-Way SLI

Setting up NVIDIA GeForce GTX 3-Way SLI was just as simple as setting up Radeon HD 7970 Tri-Fire. We installed all three GTX 680 cards and applied our 3-Way SLI bridge connector. With 3-Way SLI the bridge connector connects every single connector atop the video cards, so all six connectors are used. This bridge connector also holds the cards in place and keeps these properly aligned on the motherboard. Then, in order to setup each display to work with NV Surround the software required that we plug each display into one video card each. We used all DVI, and plugged each display into one video card. We tried to make it so that we had two displays on card 1 and one display on card 2, but the software said that wouldn't enable the third display. It said we needed to plug in a display to all three cards, so we did so, and then it worked just fine.

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In terms of software, we had no trouble using the latest NVIDIA ForceWare driver, 301.24 with 3-Way SLI and NV Surround. We installed the driver, setup NV Surround, and we were gaming within a minute with no trouble at all. NVIDIA has it together on SLI and NV Surround support.