cpu cache

[mb26]

typically.. what is the speed of modern CPU cache? (L1/L2 or just generally) it is SRAM right?
if anyone could referance what they are saying that would be helpful.

i am aiming for a 'data per second' (GB/s..) thing rather than a GHz thing.. or is that not possible?:confused:

[doctorgonzo]

L1 and L2 cache runs at the same speed as the processor, so it is dependent upon a particular processor's clock rating. Bandwidth (GB/s) isn't really appropriate since cache is used in a very specific way; it's not like data is streamed from it like a hard drive.

[mb26]

well i want some kind of comparison to other memory systems so ideally i need a GB/s type figure.. or what?

[doctorgonzo]

Is this for a school project or something? Cache memory is not really a "memory system" like SDRAM or RDRAM or Flash memory is, so direct comparisons aren't very useful. Also, not only does cache memory run at different speeds depending on the processor, but how it is accessed and used also depends on the processor.

According to data that I have read, certain Pentium 4 cores have a 256 bit-wide L2 cache, with reads occurring every clock. So a 2 GHz processor would theoretically have 2,000,000,000*256/8=64 GB/s bandwidth.

[mb26]

i'm doing a little work into memories.. and i need some general speed comparisons
http://reviews.zdnet.co.uk/hardware/processorsmemory/0,39024015,39164010-3,00.htm
has some speeds.. as far as i have read L2 cache is generally SRAM, dont know about L1?
anyway if thats the case then were talking in the range of 9GB/s.. (and 30GB/s for L1..)

[doctorgonzo]

Both L1 and L2 types of cache use SRAM.

For cache especially, raw speed levels are not enough to determine performance.