Messages in this thread | | | Date | Mon, 9 Nov 2009 20:16:08 +0000 | Subject | Re: i686 quirk for AMD Geode | From | (Lennart Sorensen) |
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On Sun, Nov 08, 2009 at 07:42:48PM +0100, Matteo Croce wrote: > There is a small advantage, but considering that GCC isn't much geode aware yet > there is stil room for improvement IMHO:
Perhaps gcc considers geode to mean geode GX[m12] not geode LX (which is newer and the one in question here).
The Geode GX line prefers i486 code to i586 code (which appears to be what -march=geode is for). I am using i486 at the moment when I build for this one.
The Geode LX is what is being discussed which is in fact mostly a K6 as far as I understand things. It seems to like i686 code, other than apparently those NOP instructions. I wonder if the K6 has those noop instructions and if not, perhaps gcc 4.4's -march=k6-3 would be the right choice. I have always suspected the LX was really a K6-3 based design (the cache sizes are a bit different, but clock speeds and instruction sets seem to match).
The Geode NX (which no one has mentioned yet) is an Athlon derived chip.
> root@alix:/usr/src/dist# ll > totale 257M > -rwxr-xr-x 1 1000 src 93K 8 nov 2009 bzip2-i586 > -rwxr-xr-x 1 1000 src 93K 8 nov 2009 bzip2-i686 > -rwxr-xr-x 1 1000 src 60K 8 nov 2009 gzip-i586 > -rwxr-xr-x 1 1000 src 60K 8 nov 2009 gzip-i686 > -rw-r--r-- 1 1000 src 256M 8 nov 2009 linux-2.6.31.5.tar > -rwxr-xr-x 1 1000 src 90K 8 nov 2009 lzma-i586 > -rwxr-xr-x 1 1000 src 94K 8 nov 2009 lzma-i686 > root@alix:/usr/src/dist# time cat linux-2.6.31.5.tar >/dev/null > > real 0m10.168s > user 0m0.030s > sys 0m1.390s > root@alix:/usr/src/dist# time ./gzip-i586 -9 < linux-2.6.31.5.tar >/dev/null > > real 5m22.331s > user 5m10.820s > sys 0m11.170s > root@alix:/usr/src/dist# time ./gzip-i686 -9 < linux-2.6.31.5.tar >/dev/null > > real 5m3.737s > user 4m51.880s > sys 0m11.510s > root@alix:/usr/src/dist# time ./bzip2-i586 -9 < linux-2.6.31.5.tar >/dev/null > > real 9m16.539s > user 9m4.410s > sys 0m11.760s > root@alix:/usr/src/dist# time ./bzip2-i686 -9 < linux-2.6.31.5.tar >/dev/null > > real 8m48.682s > user 8m34.950s > sys 0m13.260s
-- Len Sorensen
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