Introduction

I was really looking forward to testing this setup because I think it's something that's very plausible for a lot of people who have got the money to spend. Jump back a few months and we thought we'd see the HD 6990 4GB launch towards the end of last year; December was the date getting thrown around.

Instead, what happened was the HD 6970 which we thought would launch in November launched in December and the HD 6990 became a bit of a quiet card. We knew it existed, we knew it was coming, but a month turned into a much longer wait. So if you're looking for a new video card to get some holiday gaming in, you figure you'll just go down the HD 6970 path and maybe later look at the dual GPU option that AMD offer.

Initially you might have had intentions of selling off your HD 6970 and picking up a HD 6990 in its place, but what about if you bought a HD 6990 and threw that into the mix with your HD 6970? What kind of performance can this triple GPU setup offer you?

Well, that's exactly what we intend to find out. Is it worth holding onto that HD 6970 and throwing in a HD 6990 into the mix? - Priced at a similar level to the GTX 580 SLI setup, it'll indeed be interesting to see the kind of performance we get out of the setup. What will also be interesting is to see the kind of performance we get when compared to the HD 6990 4GB CrossFireX setup that makes use of four GPUs.

Before we get into the performance side of things, though, let's just quickly look at the specifications of the cards we're using today and talk about how we ran the HD 6990 4GB.

Specifications

The first thing we did was run the HIS HD 6990 4GB in AUSUM mode which puts the core in at 880MHz; the same speed as the HIS HD 6970 2GB we're using today. Then the only difference between the HD 6970 and the HD 6990 is the memory speed. So to make sure everything was running at a nice speed, we bumped the memory clock on the HIS HD 6990 4GB to 1375MHz or 5500MHz QDR, which again is the same speed as the HD 6970.

With all three GPUs running at the same speed, it was then just a matter of checking that our setup was running correctly and you can see below in the CrossFire section that indeed 3 GPUs are enabled.