That's stupid. The package size would have to be almost the size of mini ITX, in which case there's no point in having it as one package, and that's why computers are as they are. You can't just chuck faster memory at a processor and expect it to run faster, in fact current desktop CPUs can't keep up with DDR4 and DDR5 is just around the corner. for the cpu or igpu to be worthy of HBM they would need to be high performance and have a large die size, which means more heat and more distance between stuff. SRAM is lower latency than HBM, so using HBM would increase latency. cache isn't a synonym or replacement for ram, the cache merely stores stuff that is in ram, so a larger cache doesn't reduce ram usage, the reason it's done that way is because of latency, if you had a cache as an extension of ram you would have to wait to move things back to ram before clearing the cache, that would be very slow.