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Make the "target architectures" section more up to date
git-svn-id: http://svn.linuxfromscratch.org/LFS/trunk/BOOK@11760 4aa44e1e-78dd-0310-a6d2-fbcd4c07a689
This commit is contained in:
Pierre Labastie
parent
09e3f94d7c
commit
394dc3fc60
@ -63,8 +63,8 @@ cd build</userinput></screen>
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--host=$LFS_TGT \
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--prefix=/tools \
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--disable-multilib \
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--disable-nls \
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--disable-libstdcxx-threads \
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--disable-nls \<!--
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- -disable-libstdcxx-threads \-->
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--disable-libstdcxx-pch \
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--with-gxx-include-dir=/tools/$LFS_TGT/include/c++/&gcc-version;</userinput></screen>
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@ -78,15 +78,15 @@ cd build</userinput></screen>
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instead of the one in <filename>/usr/bin</filename>.</para>
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</listitem>
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</varlistentry>
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<!--
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<varlistentry>
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<term><parameter>--disable-libstdcxx-threads</parameter></term>
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<term><parameter>- -disable-libstdcxx-threads</parameter></term>
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<listitem>
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<para>Since gcc-pass1 is built without thread support, the C++
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thread library cannot be built either.</para>
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</listitem>
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</varlistentry>
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-->
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<varlistentry>
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<term><parameter>--disable-libstdcxx-pch</parameter></term>
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<listitem>
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@ -14,52 +14,37 @@
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and x86_64 (64-bit) CPUs. On the other hand, the instructions in this book are
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also known to work, with some modifications, with the Power PC and ARM CPUs. To
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build a system that utilizes one of these CPUs, the main prerequisite, in
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addition to those on the next few pages, is an existing Linux system such as an
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addition to those on the next page, is an existing Linux system such as an
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earlier LFS installation, Ubuntu, Red Hat/Fedora, SuSE, or other distribution
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that targets the architecture that you have. Also note that a 32-bit
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distribution can be installed and used as a host system on a 64-bit AMD/Intel
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computer.</para>
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<para>Some other facts about 64-bit systems need to be added here. When
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compared to a 32-bit system, the sizes of executable programs are slightly
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larger and the execution speeds of arbitrary programs are only slightly faster.
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For example, in a test build of LFS-6.5 on a Core2Duo CPU based system, the
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following statistics were measured:</para>
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<para>For building LFS, the gain of building on a 64-bit system
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compared to a 32-bit system is minimal.
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For example, in a test build of LFS-9.1 on a Core i7-4790 CPU based system,
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using 4 cores, the following statistics were measured:</para>
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<screen><computeroutput>Architecture Build Time Build Size
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32-bit 198.5 minutes 648 MB
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64-bit 190.6 minutes 709 MB</computeroutput></screen>
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32-bit 239.9 minutes 3.6 GB
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64-bit 233.2 minutes 4.4 GB</computeroutput></screen>
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<para>As you can see, the 64-bit build is only 4% faster and is 9% larger than
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the 32-bit build. The gain from going to a 64-bit system is relatively
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minimal. Of course, if you have more than 4GB of RAM or want to manipulate
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data that exceeds 4GB, the advantages of a 64-bit system are substantial.</para>
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<para>As you can see, on the same hardware, the 64-bit build is only 3% faster
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and is 22% larger than the 32-bit build. If you plan to use LFS as a LAMP
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server, or a firewall, a 32-bit CPU may be largely sufficient. On the other
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hand, several packages in BLFS now need more that 4GB of RAM to be built
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and/or to run, so that if you plan to use LFS as a desktop, the LFS authors
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recommend building on a 64-bit system.</para>
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<note><para>The above discussion is only appropriate when comparing
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builds on the same hardware. Modern 64-bit systems are considerably
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faster than older 64-bit systems and the LFS authors recommend building
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on a 64-bit system when given a choice.</para></note>
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<para>The default 64-bit build that results from LFS is considered a "pure"
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64-bit system. That is, it supports 64-bit executables only. Building a
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"multi-lib" system requires compiling many applications twice, once for a
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32-bit system and once for a 64-bit system. This is not directly supported in
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LFS because it would interfere with the educational objective of providing the
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instructions needed for a straightforward base Linux system. You can refer to
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the <ulink url="http://trac.clfs.org/">Cross Linux From Scratch</ulink>
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project for this advanced topic.</para>
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<!-- This does not appear to be valid for LFS/BLFS any more
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<para>There is one last comment about 64-bit systems. There are some older
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packages that cannot currently be built in a "pure" 64-bit system or require
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specialized build instructions. Generally, these packages have some embedded
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32-bit specific assembly language instructions that fail when building on a
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64-bit system. This includes some Xorg drivers for some legacy video cards at
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<ulink url="http://xorg.freedesktop.org/releases/individual/driver/">
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http://xorg.freedesktop.org/releases/individual/driver/</ulink>. Many of these
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problems can be worked around, but may require some specialized procedures or
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patches.</para>
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-->
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<para>The default 64-bit build that results from LFS is considered a
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<quote>pure</quote> 64-bit system. That is, it supports 64-bit executables
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only. Building a <quote>multi-lib</quote> system requires compiling many
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applications twice, once for a 32-bit system and once for a 64-bit system.
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This is not directly supported in LFS because it would interfere with the
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educational objective of providing the instructions needed for a
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straightforward base Linux system. Some LFS/BLFS editors maintain a fork
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of LFS for multilib, which is accessible at <ulink
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url="http://www.linuxfromscratch.org/~thomas/multilib/index.html"/>. But it
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is an advanced topic.</para>
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</sect1>
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@ -14,9 +14,9 @@
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<xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="foreword.xml"/>
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<xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="audience.xml"/>
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<xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="architecture.xml"/>
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<xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="prerequisites.xml"/>
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<xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="standards.xml"/>
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<xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="why.xml"/>
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<xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="prerequisites.xml"/>
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<xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="typography.xml"/>
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<xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="organization.xml"/>
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<xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="errata.xml"/>
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