| 1 | <?xml version="1.0" encoding="ISO-8859-1"?>
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| 2 | <!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
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| 3 | "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
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| 4 | <!ENTITY % general-entities SYSTEM "../general.ent">
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| 5 | %general-entities;
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| 6 | ]>
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| 7 |
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| 8 | <sect1 id="pre-architecture">
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| 9 | <?dbhtml filename="architecture.html"?>
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| 10 |
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| 11 | <title>LFS Target Architectures</title>
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| 12 |
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| 13 | <para>The primary target architectures of LFS are the AMD/Intel x86 (32-bit)
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| 14 | and x86_64 (64-bit) CPUs. On the other hand, the instructions in this book are
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| 15 | also known to work, with some modifications, with the Power PC CPU. To build a
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| 16 | system that utilizes one of these CPUs, the main prerequisite, in addition to
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| 17 | those on the next few pages, is an existing Linux system such as an earlier LFS
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| 18 | installation, Ubuntu, Red Hat/Fedora, SuSE, or other distribution that targets
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| 19 | the architecture that you have. Also note that a 32-bit distribution can be
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| 20 | installed and used as a host system on a 64-bit AMD/Intel computer.</para>
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| 21 |
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| 22 | <para>Some other facts about 64-bit systems need to be added here. When
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| 23 | compared to a 32-bit system, the sizes of executable programs are slightly
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| 24 | larger and the execution speeds are only slightly faster. For example, in a
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| 25 | test build of LFS-6.5 on a Core2Duo CPU based system, the following statistics
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| 26 | were measured:</para>
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| 27 |
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| 28 | <screen><computeroutput>Architecture Build Time Build Size
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| 29 | 32-bit 198.5 minutes 648 MB
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| 30 | 64-bit 190.6 minutes 709 MB</computeroutput></screen>
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| 31 |
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| 32 | <para>As you can see, the 64-bit build is only 4% faster and is 9% larger than
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| 33 | the 32-bit build. The gain from going to a 64-bit system is relatively
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| 34 | minimal. Of course, if you have more than 4GB of RAM or want to manipulate
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| 35 | data that exceeds 4GB, the advantages of a 64-bit system are substantial.</para>
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| 36 |
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| 37 | <para>The default 64-bit build that results from LFS is considered a "pure"
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| 38 | 64-bit system. That is, it supports 64-bit executables only. Building a
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| 39 | "multi-lib" system requires compiling many applications twice, once for a
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| 40 | 32-bit system and once for a 64-bit system. This is not directly supported in
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| 41 | LFS because it would interfere with the educational objective of providing the
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| 42 | instructions needed for a straightforward base Linux system. You can refer to
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| 43 | the <ulink url="http://trac.cross-lfs.org/">Cross Linux From Scratch</ulink>
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| 44 | project for this advanced topic.</para>
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| 45 |
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| 46 | <para>There is one last comment about 64-bit systems. There are some older
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| 47 | packages that cannot currently be built in a "pure" 64-bit system or require
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| 48 | specialized build instructions. Generally, these packages have some embedded
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| 49 | 32-bit specific assembly language instructions that fail when building on a
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| 50 | 64-bit system. This includes some Xorg drivers for some legacy video cards at
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| 51 | <ulink url="http://xorg.freedesktop.org/releases/individual/driver/">
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| 52 | http://xorg.freedesktop.org/releases/individual/driver/</ulink>. Many of these
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| 53 | problems can be worked around, but may require some specialized procedures or
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| 54 | patches.</para>
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| 55 |
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| 56 | </sect1>
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| 57 |
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