diff --git a/CMakeLists.txt b/CMakeLists.txt
index 70cc241074..9764bd591e 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -37,18 +37,24 @@ else()
   set(SCRIPT_EXT sh)
 endif()
 
+# set compiler short name and choose SSE2 option for appropriate MSVC compilers
 if (DEFINED MSVC70)
   SET(COMPILER vc7)
-  add_definitions(/arch:SSE2)
 elseif (DEFINED MSVC80)
   SET(COMPILER vc8)
-  add_definitions(/arch:SSE2)
+  if (${COMPILER_BITNESS} STREQUAL 32)
+    add_definitions(/arch:SSE2)
+  endif()
 elseif (DEFINED MSVC90)
   SET(COMPILER vc9)
-  add_definitions(/arch:SSE2)
+  if (${COMPILER_BITNESS} STREQUAL 32)
+    add_definitions(/arch:SSE2)
+  endif()
 elseif (DEFINED MSVC10)
   SET(COMPILER vc10)
-  add_definitions(/arch:SSE2)
+  if (${COMPILER_BITNESS} STREQUAL 32)
+    add_definitions(/arch:SSE2)
+  endif()
 elseif (DEFINED MSVC11)
   SET(COMPILER vc11)
 else()
@@ -68,6 +74,7 @@ else()
   add_definitions(-fexceptions -fPIC -DOCC_CONVERT_SIGNALS -DHAVE_WOK_CONFIG_H -DHAVE_CONFIG_H -DLIN)
 endif()
 
+# enable structured exceptions for MSVC
 string(REGEX MATCH "EHsc" ISFLAG "${CMAKE_CXX_FLAGS}")
 IF(ISFLAG)
   STRING(REGEX REPLACE "EHsc" "EHa" CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}")
@@ -75,13 +82,14 @@ ELSEIF(WIN32)
   SET(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -EHa")
 ENDIF()
 
+# enable parallel compilation on MSVC 9 and above
 IF(WIN32)
   IF(NOT DEFINED MSVC70 AND NOT DEFINED MSVC80)
     SET(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -MP")
   ENDIF()
 ENDIF()
 
-# warning level 4
+# increase compiler warnings level (-W4 for MSVC, -Wall for GCC)
 IF(MSVC)
   if(CMAKE_CXX_FLAGS MATCHES "/W[0-4]")
     string(REGEX REPLACE "/W[0-4]" "/W4" CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}")