kernel cpu entries
noackjr at alumni.rice.edu
Wed Dec 14 21:31:04 PST 2005
Mike Jakubik wrote:
> Mark Kirkwood wrote:
>> Is a minor update to the handbook needed in order avoid confusion
>> then? e.g. I have been commenting out CPU_I586 on all my PIII systems
>> in the (mistaken it would seem) belief that having CPU_I686 only was
> Agreed, i have always just used I686, assuming it inherited the features
> of I586. I think most people will assume this.
A quick benchmark (average of five 'dd' runs sending a large file to
/dev/null using a blocksize of 32k) similar to that suggested by Matt
Dillon (http://www.freebsd.org/projects/ideas/#p-memcpy) shows ~3%
increase with I586_CPU on a dual Pentium III. This was on a lightly
loaded live system, but I think it shows that using I586_CPU on an i686
CPU does show a performance improvement (at least in certain tests).
I have done no testing with blowfish to see how I586_CPU might affect it
as I use AES, but it seems it should be recommended for i686 CPUs as well.
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