What exactly is cache and how important is it?

So the new laptop I'm getting has 3MB of cache and my old MacBook has 6MB of cache. What exactly is cache? Is going from 6 to 3 that big of a downgrade or what?

 

Cache is like RAM but on the processor itself. There is L1, L2, and L3. The higher the level, the larger the cache is, but the slower/higher latency the access speed is. You can extend this to RAM and then the hard drive as higher, more spacious, and slower levels of memory. The cache in question is L3. More of this is good for performance, but it really varies depending on what you are doing. 3MB is enough so that going to 6MB doesn't give you a big increase in performance in most things. Don't worry about it. If the processor is at a higher frequency or a newer architecture, you are definitely not taking a step back with it.

 

Cache acts like independent memory integrated to your CPU, when needed, your CPU doesn't have to access the system memory(RAM), instead, the integrated cache is used by the CPU, which works much faster than the system memory. As for the importance of cache, it varies depends on the programs, some can somewhat benefit from a higher cache, some don't. But in general, the difference ain't significant.

It doesn't mean going to a i5-540(3M L2 cache) from a p9600(6M L2 cache) is a downgrade, the advanced and improved architecture/new added instruction set of the i-processors are much more important than the size of cache.

:Trottel beats me to it:

 

Thanks a lot, guys!

And yeah, I'm going from a Core 2 Duo to a Core i5 560.