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Athlon 64 And Intel The Way Data Travels


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It was a general FYI to show NOOBS how much farther the data has to travel in a P4 opposed to the Athlon 64 processors. No specific Intel P4 or AMD 64 was in mind, just a generalization to help visualize why Intel would be better or worse in certain areas opposed to the AMD 64...ie video encoding..etc Don't think too deep about it :P

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My P4 is so s***, I need to go AMD64. :lol:

 

Seriously, the AMD64 is growing on me. I think my next computer will have a 64-bit Athlon. My main issue; heat, seems to be solved with the AMD64. I don't like noisy fans, which is why I went with the P4 to begin with. They were easier to cool.

 

Intel seems to be dragging their asses around lately, not coming up with anything exciting.

Edited by Hyper Threaded

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AMDs core clock is faster than intels... i think thats explains the same thermal output

 

intel quad pumps there fsb (hence 800 mhz)

 

AMd double pumps there fsb (hence 400 mhz) on the 32bit.. i dunno the 64bit

 

i think red said that a while ago.. forgot the thread

What?!

 

1. AMDs run SLOWER clockspeeds than P4s.

 

2. A64s tend to run noticably cooler than P4 Prescotts (somewhat cooler than P4EEs)

 

3. AMD double pumps the FSB, Intel QUAD pumps it.

 

4. The reason that SLOWER AMDs, especially the 64s, can keep up or surpass Intels of the same speed is because of the shorter pipe, specifically: 10 steps in an AXP, 12 in the A64, while Intels use 20 steps in the original P4, and 31 for the 90nm P4.

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Plus the different number of int and floating point piplines explaines why each chip performs better in some area's.

 

I for one found the 'simplistic' diagram at the start of the thread un helpfull, as it didn't actually show the pipe's any shorter in an amd, it just had to change direction. Sure it said it's shorter but it's could be confusing if to say that and draw something else.

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I would like to state that that picture is 100% wrong

 

AMD cpus dont take "short cuts" They do how ever have shorter pipelines, which results in lower clockspeeds but faster computing.

 

While p4 has longer pipelines which result in higher clock speeds but slower computing time which is why a 2200+ = a p4 2.2ghz

 

Processors my have simular clock speeds but still outperform one another. This is caused by the clock cycle(mhz/ghz) and instructions per clock (ipc) that the cpu is able to perform... Again cpus with longer pipelines tend to have higher clock speeds. Why is this bad if the p4 has higher clock speeds and longer pipelines? The longer the pipeline the longer it takes for instructions to be processed.

 

So AMD cpu's have a shorter pipeline and lower clock speeds but higher IPC's.

 

I believe AMD's have 9ipc and P4's 6ipc

 

So get this and multiply it by the clock speed... lets say a

AMD2500+ and a 2.5ghz p4.

 

You get a PR of 15,000 on the p4(6x2500) and

You get a PR of 16,470 on the AMD (9x1830)

 

The PR is the number of instructions executed per total-cycle.

 

Now you ask why does the AMD not have better benchmark scores?

Because a lot of programs (like rendering ones) like p4's longer-pipelined architecture.

 

So dont go around saying "oh AMD takes shortcuts" and all that junk. You prolly found that stupid picture from searching for some site on google. Who ever wrote that it totally mis-informed

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CPUs virtually never achive their max instructions per clock. No reall program uses all the differnet parts of a cpu simultaniously.

 

Take the sandra ALU test as an example. Both Athlons and Pentium 4s have 3 ALUs so they can both do 3 standard integer calculations per clock under ideal conditions. The P4s tend to run at a higher clock so they score better, not by as much as you would think becasue of the longer pipeline. If a P4 (northwood) doesn't predict right and pipeline stalls it loses 20 clocks of work, an athlon XP loses 10.

 

Ars Technica has some good articals about how CPUs actualy work. Some of it is over my head, but still interesting.

 

cpuid.com has a pritty good article on the A64 architecture and compares it to the Athlon XP and P4 architecture. http://www.cpuid.com/K8/index.php

Edited by oralpain

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