diff --git a/scripts/fail-env.sh b/scripts/fail-env.sh
index a860f93a..714b6a45 100644
--- a/scripts/fail-env.sh
+++ b/scripts/fail-env.sh
@@ -19,3 +19,12 @@ export FAIL_EXPERIMENT_HOSTS=${FAIL_EXPERIMENT_HOSTS:="bigbox.informatik.uni-erl
 # A homedir-relative directory on the distribution hosts where all necessary
 # Fail* ingredients reside (see multiple-clients.sh).
 export FAIL_EXPERIMENT_TARGETDIR=.fail-experiment
+
+# Number of parallel build processes.  If unset, #CPUs+1.
+if [ -z "$FAIL_BUILD_PARALLEL" ]; then
+	if [ -e /proc/cpuinfo ]; then
+		export FAIL_BUILD_PARALLEL=$(($(egrep -c ^processor /proc/cpuinfo)+1))
+	else
+		export FAIL_BUILD_PARALLEL=2
+	fi
+fi
diff --git a/scripts/rebuild-bochs.sh b/scripts/rebuild-bochs.sh
index bfd3e4c8..41d5312e 100755
--- a/scripts/rebuild-bochs.sh
+++ b/scripts/rebuild-bochs.sh
@@ -14,6 +14,10 @@
 # - all of the previous options finally install Bochs
 #
 set -e
+# determine absolute path of this script
+SCRIPTDIR=$(readlink -f $(dirname $0))
+# env variable defaults
+source $SCRIPTDIR/fail-env.sh
 
 if [ "$1" = fail -o -z "$1" ]
 then
@@ -27,5 +31,5 @@ fi
 #export PATH=/fs/staff/hsc/bin/ccache:$PATH
 
 # even if we only rebuilt fail, we need to link and install bochs again
-nice make -j10 bochs 2>&1 | $(dirname $0)/colorize.pl 2>&1
+nice make -j$FAIL_BUILD_PARALLEL bochs 2>&1 | $(dirname $0)/colorize.pl 2>&1
 make bochsinstall