Info: What is the "Megahertz Myth"? - Overclock.net

TheSubtleKnife · 05-25-06

The megahertz myth refers to the error made by people who think performance is based only on clock speed, without taking in account of pipelining and instruction sets.

How it began:
The myth started when the PowerPC processors of Apple were up against Intel PCs. Marketers quickily started bragging about how good the Intel proccesors were, because Intel had all the big numbers, and everyone loves to buy stuff with big numbers, right? Soon the Mhz/Ghz was the only thing that consumers thought about when buying a product.

How it is: Intel introduced the Pentium 4, the fastest processer Ghz-wise, but to obtain this high speed, they had to sacrifice per clock cycle performance. As of now, Intel processors do 6 calculations per clock cycle while AMD does 9*. This effectively makes a 2Ghz AMD just as good as a 3Ghz Intel.Also, at the New York Macworld Expo Keynote on July 18, 2001, Steve Jobs described an 857 Mhz G4 as completing a task in 45 seconds while a 1.7 Ghz Pentium 4 took 82 seconds for the same task, which further proves that it is a myth. Think of it as 2 bikers, both on 10 speed bikes, one is on the top gear, peddleing very slowly, but covering alot of ground per pedal, the other guy is on the lowest gear, so he has to pedal like a maniac to cover the same distance. The 1st guy is AMD, and the second guy is Intel, where each stroke on the pedal is clock speed, and the distance traveled is performance.

How it is ending:
With Intel's new Conroe/Core 2 Duo proceccers, they dumped the Pentium 4 architecture, and like their PIII and AMD , going for lower speeds and better performance, intel now has to dig them selves out of the hole they made that faster speed means better preformance. Once intel smoothes that over, the megahertz myth will be no more. On the other hand, now that AMD is stuck with lower calcuations per second than conroe, they may be able to use the megahertz myth against intel, but who knows?

*Now with Intels new Conroe processer, it does 10-12(its not currently known) calculations per cycle; even beating AMD out 3.33-4 to 3 calculations per cycle

SoaDMTGguy wrote a program:

Quote:

Originally Posted by SoaDMTGguy

I wrote a little program that does comparisons between current AMD and Intel CPU's, to help people understand why a 2.4 GHz Core 2 Duo smokes their 3.2 GHz Pentium 4

kagaos · 06-12-06

Awesome faq! This definatly deserves a rep!

kaxx · 06-15-06

Nicely done, this will be great info for newcomers.

+REP points

sniperscope · 06-18-06

yey now I understand that!! W00T. Btw, performance is spelt performance, not preformance (I'm sure its just that one of ur fingers is faster than the other ;) lol)

ThaWaxShop · 06-18-06

But one thing... with the core duo and such they arent following in AMD's footsteps there reverting back to the old way like the PIII and dothan/banias cores. Just taking that basis and remapping it not following AMD. AMD just never tried any other way and stuck with the old way