Does CPU GHz Rating Matter?

Brent writes:

I love watching the show and how you’re opening this site for detailed questions. I have a question regarding processors (specifically for mobile devices).

With all the talk about quad-core processors in today’s devices, I’m a little confused about how the GHz of each processor comes into play.

Does a “1.6 GHz quad-core processor” mean that each of the four cores are running at 1.6 GHz? Or is the whole CPU running at 1.6 GHz? If so, is a higher GHz CPU better than a lower GHz (such as 2.3 GHz vs. 1.6 GHz)? What if you have a dual-core CPU at a higher GHz vs. a quad-core with a lower GHz?

I hope this question makes sense. I’m basically looking for a “101” on CPUs: number of cores vs. GHz.

Does CPU GHz Rating Matter?There are several different ways to approach an answer to this question. On one hand, GHz does give you an indication of exactly how powerful a processor may be, but only really in relation to other processors featuring the same technology. For example, a dual-core processor running at 2.0 GHz made this year may well smoke a quad-core processor with the same GHz rating made three or four years ago. Why? Because the technology evolves and processors become more efficient.

Each year, CPU makers develop new ways to improve the efficiency of their products. Smaller architecture, better energy handling, and driver optimization all play a role in exactly how well a CPU works.

A processor’s clock speed doesn’t take into account the efficiency of the technology. An older CPU can take a lot more clock cycles to process the same amount of data a newer CPU can handle at a fraction of the actual power draw.

Let’s say you have two processors that are part of the same generation of processors made by the same company. A core i5 Sandy Bridge quad-core processor running at 3.0 GHz will lag behind a core i5 Ivy Bridge quad-core processor running at the same GHz rating. If both of these processors were based in the same generation but have different GHz ratings, then the one with a higher number would likely crunch more data than the one with less.

It’s confusing, and this confusion isn’t made any better by the wildly different technologies being developed and used by brands like Intel and AMD. You really have to be more careful about what generation processor you’re buying than the GHz rating. Not all Core i3, i5, or i7 processors are created equal. There are multiple generations of each, and each generation has seen remarkable improvements in efficiency.

To answer your question about quad-core CPUs and what makes them different than a dual-core CPU, you can think of each core as a television set. Each set is playing a different hour-long show. You have four of them, which means you can technically watch four shows at once, but each show still takes an hour to play out. The extra core does help you get more done faster because it allows tasks to be split between four different X GHz “processors” instead of two, but that doesn’t necessarily mean you’re going to get double the amount of work done in the same amount of time.

Essentially, you have four processors running at 2.0 GHz and not one big processor running at 8.0 GHz.

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