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How Much Gets Done per Clock Cycle?

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  • Graphics
Last response: in Graphics & Displays
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September 29, 2013 4:44:36 PM

Hey guys!

I'm just curious if their was a way to answer the title question, besides using benchmarks. I first started wondering a while ago when I noticed the 8350 was significantly cheaper than the 4770k, but had a higher clock frequency and more cores. Now I understand that not each CPU gets the same amount of work done per cycle, but I'm trying to find out how to tell how much.

Thanks!

More about : clock cycle

September 29, 2013 4:53:52 PM

As far as I know, the best x86 can do is some instructions in one clock cycle. Most instructions take more cycles.

But on average AMD CPUs take more more cycles per instruction then intel counterparts lately.
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September 29, 2013 5:07:22 PM

the difference in IPC from an FX piledriver cpu and a haswell cpu is approximately 30% (roughly speaking). meaning a quad core haswell at 4.3 ghz would be about equal to a 4 core piledriver running at 5.6ghz. Assuming linear scaling on the overclocking numbers. now i know piledriver does scale linearly (bulldozer does not), i don't think i've seen enough numbers on haswell that can prove one way or another that its performance gains scale linearly (sandy bridge scaled linearly, ivy bridge sorta did... it was more of a diminishing returns thing for ivy bridge where the bottleneck shifted off the core speed to something else as you approached 5ghz)

so a i7-4770 at 4.0 ghz will perform as well as a piledriver (any piledriver) core for core running at 5.2ghz... that said all things aren't equal... piledriver cpus do come with more core which alters the equation a bit on multithreaded tasks. in an ideal situation where every app is perfectly multithreaded, using as many cores as the cpu has, an fx 8350 at 4 ghz will be about 5% faster then an haswell i7-4770k running at 4ghz with hyper threading working...

so you can see why amd is so desperate to get more things multithreaded to make use of more cores, it only helps their architecture out (especially since high overclocks are pretty easy to get with piledriver)
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September 29, 2013 5:28:31 PM

Simply put, look at benchmarks to decide what CPU is for you.
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