L2 Cache

does it make that much of a difference? My iMac G3 500Mhz L2 Cache 512 doesnt seem that much slower then my dads iMac G4 800MHz L2 cache 256. is it because the cache in my computer is twice of what his has?

It will help performance a bit, but the main advantage of the G4 is the 'velocity engine' that greatly improves performance on tasks such as media encoding, video rendering, etc.

But it just goes to show how efficient OS X can run even on older machines...