- Use select() to sleep when idle as opposed to busy waiting.

- Introduce com_busyWait cvar to go back to old behaviour

README

@@ -144,7 +144,8 @@ New cvars
   com_standalone                    - Run in standalone mode
   com_maxfpsUnfocused               - Maximum frames per second when unfocused
   com_maxfpsMinimized               - Maximum frames per second when minimized
-
+  com_busyWait                      - Will use a busy loop to wait for rendering
+                                      next frame when set to non-zero value.
   in_joystickNo                     - select which joystick to use
   in_keyboardDebug                  - print keyboard debug info
 
@@ -235,6 +236,16 @@ Using Demo Data Files
   data, nor is it something that we like to spend much time maintaining or
   supporting.
 
+Help! Ioquake3 won't give me an fps of X anymore when setting com_maxfps!
+  Ioquake3 now uses the select() system call to wait for the rendering of the
+  next frame when com_maxfps was hit. This will improve your CPU load
+  considerably in these cases. However, not all systems may support a
+  granularity for its timing functions that is required to perform this waiting
+  correctly. For instance, ioquake3 tells select() to wait 2 milliseconds, but
+  really it can only wait for a multiple of 5ms, i.e. 5, 10, 15, 20... ms.
+  In this case you can always revert back to the old behaviour by setting the
+  cvar com_busyWait to 1.
+
 QuakeLive mouse acceleration (patch and this text written by TTimo from id)
   I've been using an experimental mouse acceleration code for a while, and
   decided to make it available to everyone. Don't be too worried if you don't