2009-09-10 07:12:28 +01:00
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<?xml version="1.0" encoding="ISO-8859-1"?>
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<!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
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"http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
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<!ENTITY % general-entities SYSTEM "../general.ent">
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%general-entities;
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]>
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<sect1 id="pre-architecture">
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<?dbhtml filename="architecture.html"?>
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<title>LFS Target Architectures</title>
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<para>The primary target architecture of LFS is the 32-bit Intel CPU. If you
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have not built an LFS system before, you should probably start with that
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target. The 32-bit architecture is the most widely supported Linux system and
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is most compatible with both open source and proprietary software.</para>
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<para>On the other hand, the instructions in this book are known to work, with
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some modifications, with both Power PC and 64-bit AMD/Intel CPUs. To build a
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2009-09-10 14:58:11 +01:00
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system that utilizes these CPUs, the main prerequisite in addition to those on
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2009-09-10 07:12:28 +01:00
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the next few pages, is an existing system such as an earlier LFS system,
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Ubuntu, Red Hat/Fedora, SuSE, or other distribution that targets the system
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that you have. Also note that a 32-bit system can be installed and used as a
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host system on a 64-bit AMD/Intel system.</para>
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<para>Some other facts about a 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 are only slightly faster. For example, in a
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test build of LFS-6.5 on a Core2Duo CPU based system, the following statistics
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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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<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>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 building many applications twice, once for a 32-bit
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system and once for a 64-bit system. Currently this is not directly supported
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in the book, but is under consideration for a future release. In the meantime,
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you can refer to the <ulink url="http://trac.cross-lfs.org/">Cross Linux From
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Scratch</ulink> project for this advanced topic.</para>
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<para>There is one last comment about 64-bit systems. There are some packages
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that cannot currently be built in a "pure" 64-bit system or require specialized
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build instructions. Generally, these packages have some embedded 32-bit
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specific assembly language instructions that fail when building on a 64-bit
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system. Examples include the <ulink
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url="http://www.linuxfromscratch.org/blfs/view/cvs/">Beyond Linux From Scratch
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(BLFS)</ulink> packages Zip and some Xorg drivers. Many of these problems can
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be worked around, but may require some specialized procedures or
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patches.</para>
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</sect1>
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