Q: Let's say I have same speed, a 2.4GHz Pentium 4 CPU and a 2.4GHz Core 2 Quad CPU, performance wise, is it the latter the 4 times faster of the former one, assuming all the hardware specs the same and OS can handle multitasking?
A: No.. the number of cores don't multiply. Unless an application is specifically coded to take advatage of mutliple cores (multithreaded) then you won't see any difference between running a Core 2 Duo 2.4Ghz and Core 2 Quad 2.4Ghz - if you're multitasking a bunch of apps, you see benefits from the Quad. Compared to an older 2.4Ghz Pentium 4 CPU, even a 1.87Ghz Core 2 Duo is more than twice as fast. That's because the Core 2 chips have more efficient architecture and perform a lot more work per clock cycle. So you can't measure just by clockspeed alone. The best analogy I've found is to consider CPUs like bulldozers, and data like dirt. The older 2.4Ghz Pentium 4 chip is like a bulldozer with a 1-ton scoop, cranking along along 24 times per minute. So every minute it moves 24 tons of dirt/data. A 3.0Ghz Ghz Pentium 4 has a faster-moving arm and would move 30 tons per minute. Now ignoring the number of cores for a moment, the Core 2 chips have a larger scoop- for arguments sake let's say 3-ton capacity. So while a 1.8Ghz Core 2 cpu has a slower moving arm (only 18 times per minute) it moves 18x3 or 54 tons in the same amount of time, outperforming the higher-clockspeed Pentium 4s. In addition, you gain the benefit of multiple cores for applications which can take advantage, and lower energy consumption, lower heat output etc. Here's a CPU comparison chart: