Re: changing CHOST in stage3 (was : [gentoo-user] default stage3)
Wouldn't leaving the CHOST at i386-pc-linux-gnu build unoptimized binaries? No. Alexander Skwar Thanks for that. My CHOST flag is set to i386-pc-linux-gnu even though it is not. Just a piece of mind I guess not building unoptimized binaries. -- gentoo-user@gentoo.org mailing list
Re: changing CHOST in stage3 (was : [gentoo-user] default stage3)
To explain, keep in mind that optimisation and chost are two different things. i386 is a lowest common denominator instruction set that will run on most 386 and above x86 processors. i4/5/686 adds few specialised instructions and I believe the compiler is able to use them to produce faster code in some cases. The downside is the loss of compatibility - apparent if you switch processors. Is the system faster - my tests (done ages ago now) say yes, but not by much and its highly dependent on the actual code/data in use at the time. Generally, you will get more gain by smarter configuration, better software etc. Thats not to say optimised CFLAGS and compiler choices wont give a useful speedup, especially when crunching data. It just wont turn a 667Mhz P3 into the equivalent 1G P3 - I know I recently tried to get a little more out of one :) BillK On Wed, 2005-11-23 at 21:24 -0400, Robin wrote: Wouldn't leaving the CHOST at i386-pc-linux-gnu build unoptimized binaries? No. Alexander Skwar Thanks for that. My CHOST flag is set to i386-pc-linux-gnu even though it is not. Just a piece of mind I guess not building unoptimized binaries. -- gentoo-user@gentoo.org mailing list
Re: changing CHOST in stage3 (was : [gentoo-user] default stage3)
On Mon, 21 Nov 2005 21:08:40 -0500 Matthew Cline [EMAIL PROTECTED] wrote: | On 11/21/05, Neil Bothwick [EMAIL PROTECTED] wrote: | You can change | everything after a stage 3 install, although you have to be careful | when changing CHOST. | | I've just completed a stage3 install, and I'd like to change the CHOST | from i386-pc-linux-gnu to i586-pc-linux-gnu. I planned to do | something like this: snip | Are there any additional precautions/steps that I should take? The only way you can safely change CHOST is by making new stages through catalyst. There're various scripts which *sometimes* fix your system after a CHOST change, but they're not reliable... -- Ciaran McCreesh : Gentoo Developer (Look! Shiny things!) Mail: ciaranm at gentoo.org Web : http://dev.gentoo.org/~ciaranm signature.asc Description: PGP signature
Re: changing CHOST in stage3 (was : [gentoo-user] default stage3)
On Tue, 2005-11-22 at 17:11 -0500, Matthew Cline wrote: On 11/22/05, Alexander Skwar [EMAIL PROTECTED] wrote: Why? What do you expect to gain? The computer I am installing this on is an old Compaq laptop with a Cyrix MediaGX processor. Everything I have read suggests that this is equivalent to an i586. Am I wrong in thinking that the CHOST variable should reflect the kind of processor in the machine? Wouldn't leaving the CHOST at i386-pc-linux-gnu build unoptimized binaries? Matt I'm not an expert, but this is just copied and pasted from the gentoo handbook: The CHOST variable declares the target build host for your system. This variable should already be set to the correct value. Do not edit it as that might break your system. If the CHOST variable does not look correct to you, you might be using the wrong stage3 tarball. Cheers, Matthias -- gentoo-user@gentoo.org mailing list
Re: changing CHOST in stage3 (was : [gentoo-user] default stage3)
On 11/22/05, Matthias Langer [EMAIL PROTECTED] wrote: On Tue, 2005-11-22 at 17:11 -0500, Matthew Cline wrote: On 11/22/05, Alexander Skwar [EMAIL PROTECTED] wrote: Why? What do you expect to gain? The computer I am installing this on is an old Compaq laptop with a Cyrix MediaGX processor. Everything I have read suggests that this is equivalent to an i586. Am I wrong in thinking that the CHOST variable should reflect the kind of processor in the machine? Wouldn't leaving the CHOST at i386-pc-linux-gnu build unoptimized binaries? Matt I'm not an expert, but this is just copied and pasted from the gentoo handbook: The CHOST variable declares the target build host for your system. This variable should already be set to the correct value. Do not edit it as that might break your system. If the CHOST variable does not look correct to you, you might be using the wrong stage3 tarball. Cheers, Matthias AFAICT, CHOST is (mostly) used by portage for the --host argument to the autoconf scripts, which in turn uses it to determine the path for the tool chain. So having CHOST=i386-blah-blah means you are using the tool chain /usr/bin/i386-blah-blah-*. This is also the _default_ host that gcc will build code for. So without any -march/-mcpu/-mtune settings in CFLAGS, you will get i386 code. However, you can override that in CFLAGS, so that gcc produces i586 code by default (if that is what you want). AFAIK, there should be no difference in code produced by i586-pc-linux-gnu-gcc and i386-pc-linux-gnu-gcc -march=i586. If there is, then things like distcc should be horribly broken. -Richard -- gentoo-user@gentoo.org mailing list
Re: changing CHOST in stage3 (was : [gentoo-user] default stage3)
On 11/22/05, Richard Fish [EMAIL PROTECTED] wrote: AFAIK, there should be no difference in code produced by i586-pc-linux-gnu-gcc and i386-pc-linux-gnu-gcc -march=i586. If there is, then things like distcc should be horribly broken. Well, I've been following a related thread on gentoo-dev, and it seems I am wrong with regards to building glibc. CHOST is much more important for glibc, leading to the support (or lack thereof) of things like nptl. http://bugs.gentoo.org/show_bug.cgi?id=106556 So for getting a completely compatible i586 install, you may have to risk changing CHOST, since there is no i586 tarball available. -Richard -- gentoo-user@gentoo.org mailing list
Re: changing CHOST in stage3 (was : [gentoo-user] default stage3)
Matthew Cline schrieb: Am I wrong in thinking that the CHOST variable should reflect the kind of processor in the machine? Yes. Wouldn't leaving the CHOST at i386-pc-linux-gnu build unoptimized binaries? No. Alexander Skwar -- gentoo-user@gentoo.org mailing list
Re: changing CHOST in stage3 (was : [gentoo-user] default stage3)
Matthew Cline schrieb: I've just completed a stage3 install, and I'd like to change the CHOST from i386-pc-linux-gnu to i586-pc-linux-gnu. Why? What do you expect to gain? Alexander Skwar -- gentoo-user@gentoo.org mailing list
