What is the bandwith speed of L1,L2 and L3 Cache

zoso_the_page · July 11, 2013

Hey guys iIam sorry if was the asked the wrong way but what is the speed of the cache on a CPU

example of question SSD are 520/500GB's read/write

Ram has say 15GB's bandwith

what would the number be on the different levels of cache

again sorry I know I probably didn't explane things the right way.

leipero · July 11, 2013

Depending from CPU, L1 and L2 cache usually operate at CPU frequency, that means that speed of L1 and L2 cache depends from architecture and frequency of CPU.

L3 cache on the other hand operate at CPU-NorthBridge frequency for last generation of AMD CPU's for example, while on Intel, if I'm not mistaken, operate on CPU frequency same as L1 and L2. That means that on AMD CPU's, L3 cache have same bandwith for all Processors (as long as they have same CPU-NB frequency, and few of them don't have).

If I'm wrong about Intel, someone will correct me, maybe their L3 cache (on last generation CPU's) don't operate at CPU frequency, but i don't think that is the case.

Simple answer would be, it is different from architecture to architecture and generation/model of Processors. Hope this answer will help, but in most cases that is not relevant for any practical use, except expanding knowledge (witch is good) ;)

Glenwing · July 11, 2013

L1/L2/L3 cache are not specific designs that run at a certain speed, the speed will depend on the specific chip, usually L1 cache runs at the same speed as the chip is clocked at, and the other levels are progressively slower. The main advantage of CPU cache though, is not in bandwidth but in access time/latency, since CPU cache uses SRAMs and not slower DRAMs.