Just a dumb question

[ZeroKelvin]

Just wondering why Intel is up around 3 Ghz and Amd is around 2 Ghz. Why is the range so different yet the CPU power seem pretty close? At least from what I have been reading.

Im NOT a computer engineer so this kind of stuff baffles me.

[mata2974]

the architect and platforms are differnt

[ninthebin]

there are members who would be able to answer this better, NookieN for example...so if you dont get a good reply to this post I would probably PM and ask him. :santa2:

but I think its to do with the pipeline that data has to go down, where Intels P4 is a 20 stage pipeline, and AMDs is a 15? or something like that. So information within a longer pipeline takes longer to process so a higher clock speed suits better - now although initially this dictates IPC, I think in turn this then leads to how clock speed is dictated.

[ZeroKelvin]

I think I understand. So clock speed is a relative term is what I think your saying. Thanks for the reply.

[funnyperson1]

Clock speed is only a measure of cycles per second the Athlon processors do more work per cycle. This is mostly due to the P4s longer pipeline. When less work per cycle is done it is easier to achieve higher clock speeds and when more is done it is harder, hope this helps.

[NookieN]

Yep, the difference in clock speed is due mostly to the difference in complexity of pipeline stages. Pipelining basically means the job of performing an operation in a CPU is broken up into a series of tasks.

Instructions are stepped through the pipeline by the clock. The clock can only run as fast as the slowest (most complex) pipeline stage allows. So if stage A takes 1 ns and stage B takes 2ns, the clock can only run at 500 Mhz. If you break stage B into two stages that each take 1 ns, the chip can run at 1000 Mhz. Each instruction now takes 3 cycles to complete instead of two, but the instruction finishes in 3 ns instead of 4 ns.

Given the example above, a CPU with a longer pipeline should theoretically perform better than a CPU with a shorter pipeline. The difference in instructions per cycle between the Athlon and the P4 has to do with the number of execution units available to each. The Athlon can work on more instructions at once then the P4, but at the price of faster clock speeds.

Of course, neither approach is particularly better than the other. Longer pipelines give better performance in some situations, while more executions paths work better for others.

[ZeroKelvin]

Thanks alot NookieN. Now that I can understand a bit better. I appreciate the responses.