I study computer engineering and I read Hennessy's book about Computer Organization where it's described how the microprocessor does pipelining and that the microproceossor has on-chip cache, as much as 8 MB on-chip cache in a modern microprocessor such as AMD's Opteron. Is that on-chip cache made from SRAM or what are the physical characteristics of a modern registry file and its 2 caches, instruction and memory? Is it the same material in the L1, L2 and L3 caches?