This number grew over time , and typical CPUs now have about 512 KB , while more powerful CPUs come with 1 or 2 or even 4 , 6 , 8 or 12 MB , organized in multiple levels of a memory hierarchy . This number grew over time , and typical CPUs now have at least 512 KB , while more powerful CPUs come with 1 or 2 or even 4 , 6 , 8 or 12 MB , organized in multiple levels of a memory hierarchy .