I saw online that there is one factor that determines what cards can SLI. The GPU. This in mind, I have an EVGA GTX 650 Ti BOOST 1GB. Since this has the same GPU as the 2Gb version, could I SLI the 1Gb version and the 2Gb version?
no, dont do that.. you should SLI only the same cards with the same specifications.. it wouldn't be "oh, i have 1 gb and a 2gb card which gives me 3gb vram".. it would be like, if you have a 2gb card and another 2 gb card, it would have a good 2gb performance, not 4gb