Pentium 4 Ghz question...

[Fendrix]

Hey guys...

I was wondering if someone could help me understand the concept of GHz. I was under the impression that the more you have, the faster your CPU is. I have a Pentium 4 3.06 GHz CPU, but I've had it for almost 3 years now and I'm sure it's outdated. I really want to upgrade to an AMD 3800+ X2 but it's only 2.0 GHz... how is this possible? My computer is not fast at all, how can I have a 3.06 GHz processor and upgrade to one that is better/newer but "slower" in terms of GHz??

 

[dariob]

See this:

http://en.wikipedia.org/wiki/Hertz_Myth


Basically, a hertz is a measure of time. If a CPU can accomplish more in a hertz, then it is faster at the same clock speed as another CPU that cannot accomplish as much during that same clock speed.

 

[L0o0ky]

Lets consider the following:

My laptop has a 1.7GHz (P4 M)
My desktop at work has a 2.8GHz Northwood (P4)

I start a 7zip compression of a 6gig backup file on the desktop
15 or so minutes later, I started the same compression on my laptop.

Guess who wins....

The Laptop by a little over 15 minutes (true story). It was actually faster to copy the file across the gigabit LAN and compress it on the laptop and send it back.

Now obviously, there are a lot more factors than simple MHz/GHz going on.

 

[harpoon]

Clockspeed is only part of the picture, we also have IPC or instructiions per cycle that determine how efficient each 'MHz' is.

 

[Fendrix]

Thanks for that wikipedia article it makes more sense now.

 

[NulloModo]

Thanks for that wikipedia article it makes more sense now.

Keep in mind that clock speed does matter to a degree however. Even if one processor is faster clock for clock vs. another, if the one that is slower clock for clock ramps up the clockspeed enough, it will still perform better. For example, that Athlon64 X2 3800+ though faster clock for clock than a P4, would still get beaten by a dual core P4 running at around 3.5Ghz or so (rough estimation, could be a little less, or a little more).