Also, internal CPU caches grow over time - in 286 and before, just was not any cache; in 386 first included page cache for mmu - stores tables with mostly used pages; in next generations sometimes advertised grow of page cache.
So yes, even when your cpu could address similar size of ram, possible it don't have enough page cache for your application.
So yes, even when your cpu could address similar size of ram, possible it don't have enough page cache for your application.