Re: Dupal Opteron on Sarge
On Sat, Sep 17, 2005 at 06:49:55PM -0700, lordSauron wrote:
> pentium 4s use a 21 stage pipeline or something like that... so they
> take approximately 21 clock cycles to get anything done. AMD uses
> about 7 stages (or something in that neighbourhood) so if you divide
> 2.8 by 21 and 2.0 (my Athlon64) by 7, you get a really interesting
> breakdown. You'll certainly find a HUGE increase in performance,
That's a terrible simplification. Yes, it takes longer to get the first
result (21 cycles versus 7) but the idea of the pipeline is that you can
get a result every clock cycle after that. The latency is higher but the
throughput is also higher (more clock cycles per second).
In practice you can't use every opportunity in the pipeline, but it's
not a case of 21 clocks per instruction.
Hamish
--
Hamish Moffatt VK3SB <hamish@debian.org> <hamish@cloud.net.au>
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