Good statistics about the current install base rather than market share are hard to come by. The Steam Hardware Survey is a decent source when you're looking at

Good statistics about the current install base rather than market share are hard to come by. The Steam Hardware Survey is a decent source when you're looking at desktop PCs, because there's pretty strong overlap between desktop PC users and gamers. Slightly more than 25% of machines measured by the Steam survey don't support AVX2, which means they're pre-Haswell on the Intel side or pre-Excavator on the AMD side, or a newer but low-end Intel model. (Those recent low-end Intel chips that have AVX2 disabled also tend to have Turbo Boost disabled.) It's plausible that Sandy Bridge and earlier may still account for 10+% of gaming desktops.