diff --git a/compiler/res/prog8lib/cx16/syslib.p8 b/compiler/res/prog8lib/cx16/syslib.p8
index e18ccabeb..a0d072d3c 100644
--- a/compiler/res/prog8lib/cx16/syslib.p8
+++ b/compiler/res/prog8lib/cx16/syslib.p8
@@ -462,6 +462,8 @@ inline asmsub getrambank() -> ubyte @A {
 
 asmsub numbanks() -> ubyte @A {
     ; -- uses MEMTOP's cx16 extension to query the number of available RAM banks. (each is 8 Kb)
+    ;    Note: when 0 is returned, it doesn't mean 'zero banks', instead it means 256 banks (=2Mb banked RAM),
+    ;    as there is no X16 without at least 1 page of banked RAM.
     %asm {{
         phx
         sec
diff --git a/docs/source/building.rst b/docs/source/building.rst
index 7225359e0..592349988 100644
--- a/docs/source/building.rst
+++ b/docs/source/building.rst
@@ -202,7 +202,9 @@ You can create multiple source files yourself to modularize your large programs
 multiple module files. You can also create "library" modules this way with handy routines,
 that can be shared among programs. By importing those module files, you can use them in other modules.
 It is possible to tell the compiler where it should look for these files, by using
-the ``srcdirs`` command line option.
+the ``srcdirs`` command line option. This can also be a lo-fi way to use different source files
+for different compilation targets if you wish. Which is useful as currently the compiler
+doesn't have conditional compilation like #ifdef/#endif in C.
 
 
 .. _debugging: