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# CPU GHz

polly-gone
Okay, so I consider myself an experienced techie, as in, I can build a computer from scratch, fix computer parts, troubleshoot, fix software, etc., but, I have a question about how GHz are determined for a processor. When the speed of a processor is listed, is that the speed of each core, or is it just the speed of everything added together? How is it determined?

Like my processor is an Dual Core AMD Athlon 64 X2 5800+ Processor with a 3.0 GHz Speed. Does that mean that each core is 3.0 GHz in speed, or does it mean that each core is 1.5GHz and it adds up to 3.0?

I want to know because a friend of mine has a quad core and I want to prove that mine is better than his.

Thanks,

-Nick
ocalhoun
Well, the Ghz is a frequency, it doesn't add in this situation.

1 Hz = once oscillation per second, and 1 Ghz = 1 billion oscillations per second.
CPU's generally need two oscillations to perform one floating point operation (flop), such as adding 15+7.
So, a 2 Ghz single CPU should be about 1 Gflops (billion floating point operations per second)
A 2 Ghz dual CPU still oscillates at 2Ghz, but with both CPU's being used, it can do twice as much per operation, giving it a speed of 2 Gflops.

(As a side note, 64 bit processors are capable of doing more in one flop than 32 bit CPU's, but they otherwise operate in the same way. For example, the 64 bit CPU can add larger numbers in a single step than a 32 bit, while the 32 bit takes several flop's to do the same addition.)

flops are really a better way to measure computing power than frequency, because they can be applied to more situations: everything from your desktop to supercomputers.
ForceRun
Thats good information. If you want to compare cpus, the best way to do that is in real life sitituations. Load up a benchmark program like http://www.sisoftware.net/ Sandra 2009 or 3DMarks, and test your system. It will give you a score that you can compare to other cpus, listed in the program or online. Or you can just go to places like http://www.tomshardware.com and find their list on benchmarks.
Flakky
I don't know for sure. Intel names their processors depending on the power per core, AMD I believe adds all numbers up to look more impressive I believe.
leontius
But I heard that two cores cannot really add up to each other strength (eg. a dual core 1.7 GHz CPU does not perform as fast as a single core 3.4 GHz CPU). There are also differences between multiple core technologies, say, Intel Dual Core vs. Intel Core 2 Duo. So CPU frequency does not play that much of a role in CPU speed is it?
internetjobs
i really dont know whats the difference between dual core and core 2 duo.
recently i bought a Dell inspiron 1525. but i got it with the core 2 duo processor with 3ghz.. but my friend got dual core processor. can anyone tell me whats the exact difference between dual core and core 2 duo..
ForceRun
Just look up the benchmarks guys. http://www.tomshardware.com/charts/processors,6.html

Or the http://en.wikipedia.org/wiki/Core_2_duo for more basic info.
Flakky
 leontius wrote: But I heard that two cores cannot really add up to each other strength (eg. a dual core 1.7 GHz CPU does not perform as fast as a single core 3.4 GHz CPU). There are also differences between multiple core technologies, say, Intel Dual Core vs. Intel Core 2 Duo. So CPU frequency does not play that much of a role in CPU speed is it?

No they don't add strength when used but they can be used for syncronized calculations. Let's say that program X runs on core 1 and program Y runs on core 2. Program X is using 100% CPU at this time which means that program Y can't run on normal single core machines but program Y has the second core to it's disposal. A second advantage of dual core machines is for example a game uses 1 core for the mechanics and 1 core for the physics. The OS is 'bothering' core 1, all other applications and services running probably use core 1 as well and if a game needs to run physics and mechanics at the same time it produces lagg. Dual cores can spread load over multiple processors but the game must support dual core. If it doesn't it will probably stick to core 1.
internetjobs
thanks for the link. i got some info.. but i like to know more about this technically
Peterssidan
There must be more than just the GHz that decide how good the CPU are. I have heard that a 2 GHz AMD is at least as good as 3 GHz Intel.

So don't only look at the Gigahertz
psycosquirrel
This is true. The architecture, cache, etc all come into play to determine performance.

My Atom core is 1.7GHz, but it is faster than my old 3.2GHz Pentium 4.

To answer the original question, the GHz listed is PER CORE. They do not add in any way, as modern processors are multithreaded. If you run one program, it will only operate on one core unless it is designed to utilize both (or more).

So, for example, let's say that I have a quad-core processor at 3GHz. That means I have 4 separate processors running in unison, each running at 3GHz.
internetjobs
i am agree with this... but still we have more info, whats really the GHz do in various processor like intel, AMD, etc..
Helios
internetjobs, ocalhoun explained it basically well enough. You can always read about microprocessors and microcontrollers if you want to know more. It takes no more than a short google search.
dickyzin
It was so much easier to compare Intel CPUs during the Pentium 4 reign. We used to just look for the higher frequency (GHz) value among Pentium 4 CPUs. But somehow the frequencies were reaching its limits and they had to come up with other ways to speed things up, hence more confusion.
ocalhoun
 dickyzin wrote: It was so much easier to compare Intel CPUs during the Pentium 4 reign. We used to just look for the higher frequency (GHz) value among Pentium 4 CPUs. But somehow the frequencies were reaching its limits and they had to come up with other ways to speed things up, hence more confusion.

The same thing happened some time ago, which caused a short craze about dual-CPU's.
History is repeating itself in that when they can't get faster in frequency, they get wider, introducing multiple cores and 64 bit CPU's.

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