architecture.xml 3.1 KB

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