--- a/doc-src/System/present.tex Wed Jan 02 16:17:49 2008 +0100
+++ b/doc-src/System/present.tex Wed Jan 02 16:32:52 2008 +0100
@@ -469,14 +469,14 @@
\medskip The \texttt{-M} option specifies the maximum number of
parallel threads used for processing independent theory files
-(multithreading only works on suitable ML platforms). When tuning the
-performance of large Isabelle sessions, the number of actual CPU cores
-of the underlying hardware is a good starting point for option
-\texttt{-M}. The \texttt{-T} option determines the level of detail in
-tracing output concerning the internal locking and scheduling in
-multithreaded operation. This may be helpful in isolating performance
-bottle-necks, e.g.\ due to excessive wait states when locking critical
-code sections.
+(multithreading only works on suitable ML platforms). The special
+value of ``\texttt{0}'' or ``\texttt{max}'' refers to the number of
+actual CPU cores of the underlying machine, which is a good starting
+point for optimal performance tuning. The \texttt{-T} option
+determines the level of detail in tracing output concerning the
+internal locking and scheduling in multithreaded operation. This may
+be helpful in isolating performance bottle-necks, e.g.\ due to
+excessive wait states when locking critical code sections.
\medskip Any \texttt{usedir} session is named by some \emph{session
identifier}. These accumulate, documenting the way sessions depend on