How do we measure a CPU‘s work? Whether it‘s fast or not depends on three factors: IPC, Hz, Clock speed.
IPC means instructions per cycle, Hertz[Hz] means cycles per second and Clock speed‘s definition is always the large number of Hz.
So if two CPUs have the same Clock speeds, the one that has higher IPC is more powerful.
Furthermore, while increasing clock speed almost immediately speeds up all programs running on that computational unit,
because they are able to do more calculations per seconds(It can run more IPC), but the clock speed is unchangable
in every chip.
From the above what the I say, it seems that chip can speed up when we add more CPUs. Nowadays, because of the
prevalence of multicore architectures, we have already created a chip including multiple CPUs within a computer. However, it does
not means that the computer can run faster if we add more CPUs. Here is chart which can explains everything:
原文：http://www.cnblogs.com/zhuangzebo/p/7387846.html