Because they run neither 1:1, nor 1:2 1:2 is too penalizing on latencies, and 1:1 is almost impossible to do, as their IOD not THAT different from Zen3 and also based on 7nm iirc. Atm they run FCLK 2000 or up to 2133 iirc. So their sync to 6000 MT RAM is closer to 2:3, but it is fine even at 4:7 (aka 2000:7000). Gaining bandwith from MT doesn't hit IF bandwith limit, at least not now. Basically fact that DDR5 standard originally was about 6000MT, AMD first task in designing Zen4 was to remove dependency of MCLK and FCLK. Otherwise it would've been impossible to produce compatible chips with high enough output from wafer. And they did resolve such issue in the end. Probably they implemented same stuff that modern AMD GPU's have (well except fact that RDNA3 FCLK link is insane on both bandwith and physical size as it is very small). Atm, and you can even check it quite easily, default FCLK for GPU is about 1900-1950 (mine is 1940). And you can make it run at higher frequency. But there is barely any gain from it, even if i get it up to 2100 and even in benchmarks.