source: BOOK/final-preps/aboutsbus.xml @ 3f8be484

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<!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.4//EN"
  "http://www.oasis-open.org/docbook/xml/4.4/docbookx.dtd" [
  <!ENTITY % general-entities SYSTEM "../general.ent">
  %general-entities;
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<sect1 id="ch-final-preps-aboutsbus">
  <?dbhtml filename="aboutsbus.html"?>

  <title>About SBUs</title>

  <para>TO BE REWRITTEN</para>

  <!--
  <para>Many people would like to know beforehand approximately how long
  it takes to compile and install each package. Because Linux From
  Scratch can be built on many different systems, it is impossible to
  provide accurate time estimates.  The biggest package (Glibc) will
  take approximately 20 minutes on the fastest systems, but could take
  up to three days on slower systems! Instead of providing actual times,
  the Static Build Unit (SBU) measure will be
  used instead.</para>

  <para>The SBU measure works as follows. The first package to be compiled
  from this book is the statically-linked Binutils in <xref
  linkend="chapter-temporary-tools"/>.  The time it takes to compile
  this package is what will be referred to as the Static Build Unit
  or SBU. All other compile times will be expressed relative to this
  time.</para>

  <para>For example, consider a package whose compilation time is 4.5
  SBUs. This means that if a system took 10 minutes to compile and
  install the static Binutils, it will take
  <emphasis>approximately</emphasis> 45 minutes to build this example
  package. Fortunately, most build times are shorter than the one
  for Binutils.</para>

  <para>Please note that if the system compiler on the host is GCC-2.x based, the
  SBUs listed may be somewhat understated. This is because the SBU is
  based on the very first package, compiled with the old GCC, while the
  rest of the system is compiled with the newer GCC-&gcc-version; (which is
  known to be approximately 30 percent slower). SBUs are also not
  highly accurate for Symmetric Multi-Processor (SMP)-based machines.</para>

  <para>In general, SBUs are not entirely accurate because they depend on many
  factors, including the host system's version of GCC. Note that on Symmetric
  Multi-Processor (SMP)-based machines, SBUs are even less accurate.  They are
  provided here to give an estimate of how long it might take to install a
  package, but the numbers can vary by as much as dozens of minutes in some
  cases.</para>

  <para>To view actual timings for a number of specific machines, we recommend
  <ulink url="&lfs-root;~bdubbs/"/>.</para>
  -->

</sect1>