Are Intel or AMD processors better? This is one of the most popular questions asked by people buying a new computer. It's no wonder that choosing the best CPU might seem like a complicated process. You can't tell which one is faster by simply looking at the clock rate (raw GHz) anymore! A quad core processor won't necessarily be faster than a dual core one, either. How can you know which CPU will have the best performance then?
About 10 years ago, things were more simple. The "MHz wars" between AMD and Intel were in full swing, and a consumer knew that the CPU with a higher clock speed would be the faster one. It all changed, however, with the release of Intel Pentium 4 and AMD's answer to that, the Athlon XP. The two processors had vastly different microarchitectures which meant that the P4 could achieve much higher clock speeds, even though Athlon XP was usually significantly faster on a per-MHz basis.
For example, a 1.8 GHz Athlon XP could easily outperform 1.8 GHz (and sometimes even higher) Pentium 4. AMD was losing buyers due to their supposedly "slower" CPUs - which in reality were faster, even though they had lower clock rate. They decided to start using a Performance Rating system to compare the processor speed instead of advertising the raw MHz. Funnily enough, Intel soon hit the limit on the P4 architecture and followed AMD's example. Nowadays all CPUs use some form of PR system as a performance measure.