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Is CPU speed/performance judged by its GHZ ?

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November 12, 2011 1:46:26 AM

so I am browing ebay for PCs

the higher the ghz the faster it is ??

and if it is dual core then 2 x 2 ghz = 4ghz ? etc etc


Is this correct ?


Whenever I buy a graphics card though I always look on the 'graphics card hierarchy'
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November 12, 2011 2:10:11 AM

You can only compare CPUs based on clock speed if they are in the same family, like a Phenom II X4 945 @ 3.0 GHz will be slower than a 980 @ 3.7 GHz, but the Phenom II 980 @ 3.7 GHz will get beat by an Intel i5 2500 that is only running at 3.3 GHz.

Architecture contributes far more to how well a CPU performs than does its clock speed, we have hit the ceiling for clock speeds, they haven't increased much since in the Pentium 4 era, but the amount of instructions done per clock cycle increases with every generation of CPU. Tom's has a CPU hierarchy chart to help with comparisons.


Also, a dual core at 2 GHz has 2 cores that each run at 2 GHz, this is NOT equivalent to a single core that runs at 4 GHz. Each core runs a single thread(assuming hyperthreading is disabled), so if you are only running a program with a single thread a dual core isn't going to be able to do it faster than a single core which is why you don't just get to multiply cores by clock speed.
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November 12, 2011 2:45:00 AM

Dual core at 2.0Ghz is not 2 x 2 = 4.0Ghz. I've seen many people reference a highway for this. If your speed is 55mph and you have a single lane, all traffic moves at 55mph, if you have 2 lanes, traffic still runs at 55mph but you can have twice the traffic. Traffic doesn't mysteriously run at 110mph.

Clock speed is only relevant for the same cpu family. Back in the day a 2.0Ghz Athlon was faster than a 3.0Ghz Pentium 4. A 2.6Ghz Core2Duo was faster than a 3.0Ghz Athlon X2. Currently a 3.3Ghz I5 is faster than a 3.7Ghz Phenom II. It would be best to look at some CPU benchmarks before making a purchase.
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November 12, 2011 1:16:03 PM

half of those CPUs in the hierarchy are not even in the ebay listings

so how do I know ?
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November 12, 2011 2:14:14 PM

Back in 1823 they had the GHZ wars when the P4 was still running around. Today is more about whos architecture is the most efficient per watt
November 12, 2011 2:16:36 PM

okay

what is the cheapest CPU that will play all modern games ??

So my question is is simply, the cheapest but best CPU ?

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November 12, 2011 2:21:28 PM

fuggles said:
okay

what is the cheapest CPU that will play all modern games ??

So my question is is simply, the cheapest but best CPU ?

For games the gpu is more important.
At 1080p most quads are able to keep pace with any gpu.
Best bang for buck choices are the X4 955BE 105usd or the I3 2100 going for around 120usd depending on if your a Intel or Amd fan.
How much is your budget?
November 12, 2011 10:15:35 PM

my budget is 200 UK British pounds , which I think is 400 USD

I don't know much about custom made computers, I mostly look on ebay



I want

4 gb of ram
dual core processor that is good enough
9800gt graphics card I already have anyway

Currently I have 2gb of ram and a
pentium 4
!