diff --git a/doc/how-to-build.txt b/doc/how-to-build.txt
index eb2c3a1b..94657ac7 100644
--- a/doc/how-to-build.txt
+++ b/doc/how-to-build.txt
@@ -27,6 +27,7 @@ Required for the gem5 simulator backend:
  - zlib
  - m4
  - python-dev
+ - optional: libgoogle-perftools-dev
 
 For distribution/parallelization:
 **********************************************************************
@@ -205,6 +206,12 @@ TODO: Fix Hard-coded paths
 Building gem5:
 **********************************************************************
 
+Fail* configuration:
+------------------------------------------------------------
+ - BUILD_GEM5 ON
+ - all configuration options specific for other simulators OFF
+ - COMPILER: gcc (not ag++)
+
 For the first time:
 ------------------------------------------------------------
  1. Change to the gem5 simulator directory (expects to be in ${FAIL_DIR}):
@@ -216,8 +223,10 @@ Optimized build:
 ------------------------------------------------------------
       $ cd ../simulator/gem5
       $ scons EXTRAS=../../src/core/sal/gem5 build/ARM/gem5.fast
+(add -jN for a parallel build)
 
 Debug build:
 ------------------------------------------------------------
       $ cd ../simulator/gem5
       $ scons EXTRAS=../../src/core/sal/gem5 build/ARM/gem5.debug
+(add -jN for a parallel build)