General issues/problems to consider using multiple graphic cards in SLI

Question

The objective of this question is to discuss any major issues, problems, considerations in using 2+ GFX cards in SLI.

There are some specific questions on SuperUser about, making use of PHYSX (and this), multiple monitors, and some about the actual OS being used i.e. WinXP.

The common consideration factors are:

• Hardware - a suitable motherboard.
• Power - having the right power supply
• Cost - bang for buck, SLI vs Single-Top-End-GFX-Card, setup effort & time.
• Performance - what you actually gain from SLI

For these items there are lots of hardware review articles, but please add links if there are some exception articles.

I'm looking to see if there are any other issues to consider, in particular:

• Compatibility with OSes, Games and Applications.
• Ease of disabling SLI if necessary (open case and remove connector/power of 1 card or software option)
• Any recommendations people have from personal experience.

Answer 1

From personal experience I would say to make sure your cooling setup is adequate. I used to run SLI with two watercooled cards, but one day switched to two air cooled cards. Problem was that my case wasn't set up to move much air around where the cards were and they overheated a ton.

As for disabling SLI, it's simply a matter of checking a box on the NVIDIA control panel, no need to open the case. You can even specify on a per application basis whether to use it or not.

That said, I still run into hardware issues every once in a while where one card will fail and I'll feel like I'm not getting the most bang for my buck. I once had the power sensors fail on my cards so they would underclock themselves and be rather slow.

I rarely have compatibility issues as long as I'm running the latest NVIDIA drivers. Sometimes older or poorly supported games have a performance issue, but it's usually pretty obvious (screen is flickering or acting in a strange manner) and it's easy to check since sli can be disabled simply.

If you're thinking of getting an SLI set up right now I'd say wait a month or two. There hasn't been a top line NVIDIA card released in a while and you should see one at the end of 2009 or early 2010. It's just a lot easier to maintain one card and nice to know you the newest model if you plan on spending a lot of graphics.

One last thing, if you're going to spend a lot on graphics make sure you have a monitor to handle it. If you aren't running at a very high resolution (such as 2560x1600) high end cards aren't going to make much of a difference. It's really easy to see this with some high-end SLI setups when you can disable SLI and not notice any dip in framerate.