[mythtv-users] Re: Problems using MythTV - errors with channel
parameters
Joseph A. Caputo
jcaputo1 at comcast.net
Wed Jan 26 10:10:34 EST 2005
On Wednesday 26 January 2005 2:12, Michael Obster wrote:
>
> > As for reading GCC Documentation, what about it? Did you ever think
that
> > maybe... just maybe... the build environment might be optimizing for
the
> > specific platform you are compiling on? Jeez.
>
> Thats the point. There are many build kits out which do optimization
for
> specific architectures. For example look at Gentoo or ROCK Linux. The
> build system optimizes the complete build environment for a selected
> cpu. The only exception on x86 is pentium 4, because this is still
> experimental *g*.
> If you look at the assembler output ,gcc creates, there is much
> difference between the different platforms. For example parallel
working
> on cpu registers, using SSE, using 3dnow or mmx and so on. Also a
speed
> up is between this different optimization.
> This features are in the gcc documentation for example ;-).
> A hardcoded -march=pentiumpro does not recognizes such things, even I
> know qmake is a little bit tricky here. Personally I prefer autotools
> for building software.
> So to get an optimal optimization, it is better to let the build
> determine which option is needed ;-).
Actually, if you read through the mailing list archives you'd find that
-march=pentiumpro actually generates better performing object code than
some of the more processor-specific (i.e., -march=athlon-xp)
optimizations. It all has to do with the type of operations being
performed.
Also, as far as non-x86 architectures are concerned... MythTV is not
supported "out of the box" for anything other than Linux on x86. There
is an ongoing effort to support Mac OS X out of the box, as you'll see
if you examine the settings.pro file. As for other architectures like
Linux PPC or *BSD, I believe most of the code has been patched (mostly
endianness issues), but the build configuration is not supported by
default (yet).
-JAC
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