Re: About VMX/Altivec support in Debian ppc64 port
On Sat, Feb 16, 2013 at 12:07:09AM +0800, Liang Guo wrote:
> I'm working to run Debian ppc64 ports on my xbox360 box, but
> failed to setup a chrooted environment with "Illegal instruction"
> error. After some dig on this problem, I found this is caused
> by PowerPC vector instrunctions, and according to the build
> log[1], the package do compile with " -maltivec -mabi=altivec ".
>
> So I want know, why we use "-maltivec" in PPC64 ports, is
> it faster then altivec disabled? After all, many old Power4/5,
> and qemu ppc64 simulator don't support altivec.
>
> According Debian ppc64 wiki page[2], xenon, the cpu used by
> xbox360, supports altivec, but altivec don't work in my box,
> I think it is another bug or misconfigure.
>
> I'm not a subscriber of this list, please CC me.
>
> [1] http://buildd.debian-ports.org/status/fetch.php?pkg=util-linux&arch=ppc64&ver=2.20.1-5.3&stamp=1355261928
> [2] http://wiki.debian.org/PPC64
Why not run the normal ppc version? After all in general there shouldn't
be anything gained using 64bit on powerpc, especially since you have
way less than 4GB ram. The code size increase from the larger pointers
will probably hurt performance instead.
I believe the ppc64 port has chosen a baseline that requires altivec
which means if you don't have it, stick with plain ppc.
Certainly altivec is a useful feature if you have it so enabling it
makes sense.
--
Len Sorensen
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