diff --git a/compiler/res/prog8lib/cx16/syslib.p8 b/compiler/res/prog8lib/cx16/syslib.p8
index e18ccabeb..94f965a78 100644
--- a/compiler/res/prog8lib/cx16/syslib.p8
+++ b/compiler/res/prog8lib/cx16/syslib.p8
@@ -460,13 +460,23 @@ inline asmsub getrambank() -> ubyte @A {
     }}
 }
 
-asmsub numbanks() -> ubyte @A {
+asmsub numbanks() -> uword @AY {
     ; -- uses MEMTOP's cx16 extension to query the number of available RAM banks. (each is 8 Kb)
+    ;    Note that the number of such banks can be bigger than 255 so a word is returned, but mostly
+    ;    the A register could suffice as the lsb.
+    ;    The maximum number of banks is 256 = 2 Megabytes of banked Ram aka Hiram. (Y=1 and A=0 in this case).
+    ;    MEMTOP itself reports 0 in this case which we change into 256 for convenience.
+    ;    It reporting 0 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
         jsr  c64.MEMTOP
-        plx
+        ldy  #0
+        cmp  #0
+        bne  +
+        iny
++       plx
         rts
     }}
 }
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:
diff --git a/examples/cx16/diskspeed.p8 b/examples/cx16/diskspeed.p8
index 2bdefcb34..c5d8a2657 100644
--- a/examples/cx16/diskspeed.p8
+++ b/examples/cx16/diskspeed.p8
@@ -10,6 +10,10 @@ main {
     const ubyte REPEATS = 2
 
     sub print_speed(uword jiffies) {
+        if jiffies==0 {
+            txt.print("\n 0 jiffies measured, speed is extremely high\n")
+            return
+        }
         float speed = 65536.0 * REPEATS / (jiffies as float / 60.0)
         txt.nl()
         txt.print_uw(jiffies)