Ménage à trois – why?
So here we are today with 3-way SLI, Nvidia’s latest attempt to increase the number of GPUs in your system, but the question is... why do you need a technological ménage à trois in your rig?
Nvidia outlines a few reasons in fact, but arguably the biggest reason is that monster that goes by the name Crysis
. It’s a game that eats shader horsepower for breakfast, lunch and dinner before spitting them all out in a bout of drunken laughter. You simply can’t enjoy Crysis
at playable frame rates with all the details turned up to ‘Very High’ at resolutions much higher than 1280x1024 on a single card and don’t even start thinking about anti-aliasing.
In order to get smooth frame rates at 1680x1050 or 1600x1200 with ‘Very High’ settings, you’re going to need at least a pair of GeForce 8800 GTs – if not a pair of 8800 GTXs. Three-way SLI comes in at higher resolutions like 1920x1200 and 2560x1600 with the latter being a resolution where you’re probably still
going to have to make some compromises to image quality.
Crysis is an absolute beast on 'Very High' settings and is one of the driving forces behind 3-way SLI
Other reasons that Nvidia cites include being able to play every other major release out this year at 2560x1600 4xAA 16xAF with playable frame rates and, in most cases, this will mean at least a 60 fps average. That’s a pretty big claim to make and it’s something we’re going to be testing over time – unfortunately, due to the amount of time we’ve had with the hardware though, we’ve only been able to test a select few games in time for this particular article.
Preparing for Triple Time
As we outlined on the first page, 3-way SLI requires a seriously deep pocket for just the graphics card and displays alone, but it’s important not to skimp in any other area of your system. The most important component to consider, even before the graphics cards and monitor is a decent power supply because three graphics cards is going to chew up some serious power.
Nvidia recommends a minimum of a 1100W (yes, that’s eleven hundred
Watts) and with that you’ll need at least six six-pin PCI-Express power connectors. There is an approved list of power supplies over on Nvidia’s SLIZone website
which is updated as and when new power supplies are certified for 3-way SLI. The current list that Nvidia supplied us with includes ten units, but the unit we have used for our testing—Thermaltake’s ToughPower 1500W behemoth—wasn’t on the list and worked fine.
That's the south bridge right under there (right) – Click to enlarge
The other really important thing to consider with 3-way SLI is that your case can not only support three full-length PCI-Express cards that are each just over 270mm long, but to also ensure these cards are cooled adequately. Make no mistake here, because without proper cooling, your graphics cards will overheat.
Nvidia says that new thermal requirements are in place for 3-way SLI and the company will continue to test and approve new cases for 3-way SLI as and when they’re submitted for certification. Currently, the list includes just two cases – these are the Cooler Master Cosmos
and the Silverstone TJ10. I’m slightly surprised not to see the Cooler Master Stacker on that list, because for all intents and purposes, its cooling capabilities are pretty awesome even today.
Here's the 3-way SLI connector - we've added the data path arrows on to show you how data flows across the three GPUs
Once you’ve got yourself a decent power supply and case, it’s time to start thinking about the rest of your system. In order to complement the three high-end graphics cards and the nForce 680i SLI motherboard, you’re going to want a CPU that is as fast as possible in order to limit the number of cases where you will be CPU-limited for example. Naturally, Nvidia recommends pairing a 3-way SLI configuration on nForce 680i SLI with the Core 2 Extreme QX6850—the fastest chip that the platform supports—but you could easily get away with a Core 2 Quad Q6600 and a bit of overclocking
The final thing you’re going to need once you’ve got all of these components is of course an SLI connector that is specifically designed for 3-way SLI. Nvidia tells us that you will be able to buy one of these separately for around £13 (inc. VAT) on Scan
if you’re an nForce 680i SLI owner and Nvidia’s next-generation motherboards will come with one supplied in the retail bundle.