AMD Sempron CPUTYPE & Co.

Andrew P. infofarmer at gmail.com
Thu Sep 22 00:23:53 PDT 2005


On 9/22/05, jason <jason at ec.rr.com> wrote:
> Andrew P. wrote:
>
> >Hello!
> >
> >So I have a Sempron 2500+ CPU, one that supports
> >SSE3. What should I place in my /etc/make.conf? I use
> >ssh with X11Forward very often, so OpenSSL should
> >be compiled to be as fast as it can be on this CPU.
> >Here's a part of dmesg:
> >
> >CPU: AMD Sempron(tm) Processor 2500+
> >(1407.05-MHz 686-class CPU)
> >Origin = "AuthenticAMD"  Id = 0x20fc2  Stepping = 2
> >
> >  Features=0x78bfbff<FPU,VME,DE,PSE,TSC,MSR,
> >PAE,MCE,CX8,APIC,SEP,MTRR,PGE,MCA,CMOV,
> >PAT,PSE36,CLFLUSH,MMX,FXSR,SSE,SSE2>
> >  Features2=0x1<SSE3>
> >  AMD Features=0xe2500800<SYSCALL,NX,MMX+,
> ><b25>,LM,3DNow+,3DNow>
> >
> >I want to use SSE3, but I don't want to set CPUTYPE
> >to nocona, cause that way compilers won't ever use
> >AMD features. Is there a way to tell compilers to use
> >every feature I've got?
> >
> >
> >Thanks very much,
> >Andrew P.
> >_______________________________________________
> >freebsd-questions at freebsd.org mailing list
> >http://lists.freebsd.org/mailman/listinfo/freebsd-questions
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> >
> >
> >
> man make.conf and man gcc
>
> You will be limited by the gcc version on FreeBSD.  You can use gcc 4
> for your apps, and all that SSE and 3DNow  stuff is not currently
> allowed in the kernel.
>
> I remember ready, maybe on slashdot, where a man did very little work to
> do a native port of ssh to native amd64 code and got a hugh speed
> boost.  Making sure you get a optimized version os ssh like what I
> described will make a much bigger difference than just adding amd64 as
> your cp type to make.conf.
>
> Jason

I run FreeBSD/i386, not amd64.

make.conf, gcc and cpp manpages tell you nothing about
the subj. I roamed mailing lists for a few hours and settled on
adding "-march=pentium4 -msse3" to CFLAGS and COPTFLAGS.
I didn't do any serious benchmarking, but the `top` output feels
like sshd got 2-3% performance boost. Will try to recompile
with "-mfpmath=sse" later.

Also, I tried forwarding X11 over network without SSH, and
some things kept lagging. My guess is network connection
and my solution is a Gigabit switch; the funny thing is that
I have Gb NICs in most of my PCs, but I still use a 100Mb
switch.


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