It is explained in the "get started here" thread at the top of this forum. http://isiforums.net/f/showthread.php/5304-Get-Started-Here-(how-to-purchase-faq-etc)
So do you have a recommendation for particular systems. For instance I have a 965 black edition amd quad core processor and a single 560 ti gpu. Would I benefit more from either one or do I just need to try each and see if I notice a difference. I currently have it set to none as that was the default option when I checked it.
Try them all and see which works best for you, I personally have never seen any real difference with any of the options, the game runs fine under them all for me, I do check after every new version though just in case.
I would suggest no sync at all to start with. If you notice stuttering or slo-mo, try GPU sync; it seems to work wonders.
