Specifications

Computer Architecture and Maintenance (G-Scheme-2014)

and at RAM speed about 1% (10% of 10%) of the time (16 MHz in this case). You can

clearly see the importance of both the L1 and L2 caches; without them the system uses

main memory more often, which is significantly slower than the processor.

Important Point to be noted.

Spending money doubling the performance of either the main memory (RAM) or

the L2 cache, which would you improve? Considering that main memory is used

directly only about 1% of the time, if you doubled performance there, you would

double the speed of your system only 1% of the time! That doesn’t sound like enough

of an improvement to justify much expense. On the other hand, if you doubled L2

cache performance, you would be doubling system performance 9% of the time, which

is a much greater improvement overall. I’d much rather improve L2 than RAM

performance. The same argument holds true for adding and increasing the size of L3

cache, as many recent processors from AMD and Intel have done.

The processor and system designers at Intel and AMD know this and have devised

methods of improving the performance of L2 cache. In Pentium (P5) class systems, the

L2 cache usually was found on the motherboard and had to run at motherboard speed.

Intel made the first dramatic improvement by migrating the L2 cache from the

motherboard directly into the processor and initially running it at the same speed as

the main processor. The cache chips were made by Intel and mounted next to the main

processor die in a single chip housing. This proved too expensive, so with

the PentiumII, Intel began using cache chips from third-party suppliers such as Sony,

Toshiba, NEC, and Samsung. Because these were supplied as complete packaged chips

and not raw die, Intel mounted them on a circuit board alongside the processor. This is

why the Pentium II was designed as a cartridge rather than what looked like a chip.

Q.Comparision of Cache Memories

Prepared By – Prof. Manoj.kavedia (9860174297 – 9324258878 ) (www.kavediasir.yolasite.com)