| 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 and ARM CPUs. To
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| 16 | build a system that utilizes one of these CPUs, the main prerequisite, in
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| 17 | addition to those on the next page, is an existing Linux system such as an
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| 18 | earlier LFS installation, Ubuntu, Red Hat/Fedora, SuSE, or other distribution
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| 19 | that targets the architecture that you have. Also note that a 32-bit
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| 20 | distribution can be installed and used as a host system on a 64-bit AMD/Intel
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| 21 | computer.</para>
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| 22 |
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| 23 | <para>For building LFS, the gain of building on a 64-bit system
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| 24 | compared to a 32-bit system is minimal.
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| 25 | For example, in a test build of LFS-9.1 on a Core i7-4790 CPU based system,
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| 26 | using 4 cores, the following statistics 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 239.9 minutes 3.6 GB
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| 30 | 64-bit 233.2 minutes 4.4 GB</computeroutput></screen>
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| 31 |
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| 32 | <para>As you can see, on the same hardware, the 64-bit build is only 3% faster
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| 33 | and is 22% larger than the 32-bit build. If you plan to use LFS as a LAMP
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| 34 | server, or a firewall, a 32-bit CPU may be largely sufficient. On the other
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| 35 | hand, several packages in BLFS now need more that 4GB of RAM to be built
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| 36 | and/or to run, so that if you plan to use LFS as a desktop, the LFS authors
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| 37 | recommend building on a 64-bit system.</para>
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| 38 |
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| 39 | <para>The default 64-bit build that results from LFS is considered a
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| 40 | <quote>pure</quote> 64-bit system. That is, it supports 64-bit executables
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| 41 | only. Building a <quote>multi-lib</quote> system requires compiling many
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| 42 | applications twice, once for a 32-bit system and once for a 64-bit system.
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| 43 | This is not directly supported in LFS because it would interfere with the
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| 44 | educational objective of providing the instructions needed for a
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| 45 | straightforward base Linux system. Some LFS/BLFS editors maintain a fork
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| 46 | of LFS for multilib, which is accessible at <ulink
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| 47 | url="http://www.linuxfromscratch.org/~thomas/multilib/index.html"/>. But it
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| 48 | is an advanced topic.</para>
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| 49 |
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| 50 | </sect1>
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