+ <para>Omitting <replaceable>x</replaceable>,
+ i.e. <literal>+RTS -N -RTS</literal>, lets the runtime
+ choose the value of <replaceable>x</replaceable> itself
+ based on how many processors are in your machine.</para>
+
+ <para>Be careful when using all the processors in your
+ machine: if some of your processors are in use by other
+ programs, this can actually harm performance rather than
+ improve it.</para>
+