L4 cache and location

yq know if this were like a take home test question and the instructor wanted you to think about it on a current system that only has L3 cache. Well if you think about it, what would you consider L4 cache. Ram, Virtual ram, or your HDD are your choices students. lol
 
Many text books do ever expanding levels of cache, my microcomputer systems book listed Remote storage as L6 cache, but it also only believed that CPUs had L1 cache onboard. L3 cache in older systems would have referred to the RAM or main memory, and since CPUs now have L3 cache onboard, RAM would become your L4 cache as far as a text book would be concerned.