What exactly does SLI mean and what does it do. All I know is that it has something to do with 2 GPUs, but does it make them faster or what. Are two 256mb cards in SLI better than a single 512mb card?

Can someone explain this without too much jargon please.

SLI is a feature of nVidia video cards to make two cards work together to take turns rendereing every other frame your monitor shows, every other pixel line, and such. If you have a motherboard that is "SLI-enabled", then it will have two video card slots and a small chip ("Bridge") that connects the two cards. Basically, they work together to share the work and make your games run better.

In other words, double the video cards to get better performance. However, this generally does not provide enough improvement to be worth paying for 2 video cards instead of one. With the exception of UT2004, I found that the using SLI provides a 10%-20% framerate increase when compared to using a single video card.

As for whether a single 512MB card is better than two 256MB cards, the answer is definately "maybe". If you're not messing with multiple monitors, then it does provide a difference. not as large as I would like, but definately noticable. Be advised that you can't really make a good buying decision without learning a bit of jargon such as pixel pipelines and clock speeds.

One major disadvantage of SLI is that you cannot run multiple monitors at the same time when SLIi is in use. However, two video cards with two monitr plugs each can run 4 monitors at once. Also, you can enable or disable the SLI ability in Windows (may require reboot). If you ahve a single monitor and disable SLI, one of your cards is just going to waste.

I would advise you just get a single GPU unless two SLI cards are cheaper than one that is slightly more powerful. After having used two GeForce7900GS and comparing them to other cards my friends have, a single better card would be more bang for your buck.

SLi is two video cards of the same architecture that work together on a particular task, which is rendering graphics.

And don't be fooled by big memory numbers. A slow card with 128 MB vRAM would be no better with 512, even worse if anything.

Anyway, my advice is: Stay away from SLi or Crossfire. They are nothing but a waste of money and computer resources. If you have a slow card, then save up for a single-GPU upgrade instead of wasting what you've already collected on another copy of the old card.

really? hmm... I have a PowerColor Radeon 1950 PRO PCI express card... would it be worth the money to go crossfire with this card?

No.

Thanks for the advice - at some point sone my new comp is arriving with its 880GTX.

All I can say is I am not paying for a second computer untill the new one is literally dead. Afterall, £800 is a lot for a 16 year old...

That 8800 GTX is going to last you for many many years, assuming it doesn't die from overheating or stuff like that.

Its going to haunt my bank balance for many years as well. But seriously, I decided this time that I was going to get somethig good, rather than something cheap.

@bjossi.. thanks for the answer to my question

I agree with Bjossi. SLI does not provide that a BIG difference, especialy if you are using one of the high end cards anyway.

Check out http://www.tomshardware.com and look at the VGA charts, they have normal and SLI comparisions. Makes for very interesting reading...

You know, the 8800 GT gets very close to the performance of the GTX, without breaking the bank. It only falters when you try to run at super-high resolutions or turn AA up too high.

And then Riva Tuner can pick up some of the slack with overclocking.