diff --git a/chapter04/aboutsbus.xml b/chapter04/aboutsbus.xml
index dccf59fe7..a442c20ab 100644
--- a/chapter04/aboutsbus.xml
+++ b/chapter04/aboutsbus.xml
@@ -26,9 +26,9 @@
   unit of time.</para>
 
   <para>For example, consider a package whose compilation time is 4.5
-  SBUs. This means that if your system took 10 minutes to compile and
+  SBUs. This means that if your system took 4 minutes to compile and
   install the first pass of binutils, it will take
-  <emphasis>approximately</emphasis> 45 minutes to build the example package.
+  <emphasis>approximately</emphasis> 18 minutes to build the example package.
   Fortunately, most build times are shorter than one SBU.</para>
 
   <para>SBUs are not entirely accurate because they depend on many
@@ -36,6 +36,36 @@
   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>On some newer systems, the motherboard is capable of contolling 
+  the system clock speed. This can be controlled with a command such as
+  <command>powerprofilesctl</command>. This is not available in LFS, but 
+  may be available on the host distro. After LFS is complete, it can be
+  added to a system with the procedures at the
+  <ulink url='&blfs-book;sysutils/power-profiles-daemon.html'>
+  BLFS power-profiles-daemon</ulink> page.
+
+  Before measuring the build time of any package it is advisable to use a
+  system power profile set for maximum performance (and maximum power 
+  consumption). 
+
+  Otherwise the measured SBU value may be inaccurate because the 
+  system may react differently when building <xref linkend='ch-tools-binutils-pass1'/>
+  or other packages.
+
+  Be aware that a significant inaccuracy can still show up even if the same
+  profile is used for both packages because the system may respond slower if
+  the system is idle when starting the build procedure. Setting the power
+  profile to <quote>performance</quote> will minimize this problem.  And
+  obviously doing so will also make the system build LFS faster.</para>
+
+  <para>If <command>powerprofilesctl</command> is available, issue the
+  <command>powerprofilesctl set performance</command> command to select
+  the <literal>performance</literal> profile.  Some distros provides the
+  <command>tuned-adm</command> command for managing the profiles instead of
+  <command>powerprofilesctl</command>, on these distros issue the
+  <command>tuned-adm profile throughput-performance</command> command to
+  select the <literal>throughput-performance</literal> profile.</para>
+
   <note>
     <para>When multiple processors are used in this way, the SBU units in the
     book will vary even more than they normally would.  In some cases, the make
@@ -44,10 +74,11 @@
     interleaved.  If you run into a problem with a build step, revert to a
     single processor build to properly analyze the error messages.</para>
 
-    <para>The times presented here are based upon using four cores (-j4). The
+    <para>The times presented here for all packages 
+    (except <xref linkend='ch-tools-binutils-pass1'/> which is based on one core)
+    are based upon using four cores (-j4). The
     times in Chapter 8 also include the time to run the regression tests for
     the package unless specified otherwise.</para>
-
   </note>
 
 </sect1>
diff --git a/chapter05/binutils-pass1.xml b/chapter05/binutils-pass1.xml
index 39365477d..f6b7f0f90 100644
--- a/chapter05/binutils-pass1.xml
+++ b/chapter05/binutils-pass1.xml
@@ -5,7 +5,7 @@
   %general-entities;
 ]>
 
-<sect1 id="ch-tools-binutils-pass1" role="wrap">
+<sect1 id="ch-tools-binutils-pass1" role="wrap" xreflabel="binutils-pass1">
   <?dbhtml filename="binutils-pass1.html"?>
 
   <sect1info condition="script">