diff --git a/gcode.c b/gcode.c
index d8abaf6..eeaa433 100644
--- a/gcode.c
+++ b/gcode.c
@@ -179,6 +179,7 @@ uint8_t gc_execute_line(char *line)
         switch(int_value) {
           case 0: case 1: case 2: case 30: group_number = MODAL_GROUP_4; break;
           case 3: case 4: case 5: group_number = MODAL_GROUP_7; break;
+          case 7: case 8: case 9: group_number = MODAL_GROUP_8; break;
         }        
         // Set 'M' commands
         switch(int_value) {
diff --git a/gcode.h b/gcode.h
index 8c20957..334c78a 100644
--- a/gcode.h
+++ b/gcode.h
@@ -38,7 +38,8 @@
 #define MODAL_GROUP_5 6 // [G93,G94] Feed rate mode
 #define MODAL_GROUP_6 7 // [G20,G21] Units
 #define MODAL_GROUP_7 8 // [M3,M4,M5] Spindle turning
-#define MODAL_GROUP_12 9 // [G54,G55,G56,G57,G58,G59] Coordinate system selection
+#define MODAL_GROUP_8 9 // [M7,M8,M9] Coolant control
+#define MODAL_GROUP_12 10 // [G54,G55,G56,G57,G58,G59] Coordinate system selection
 
 // Define command actions for within execution-type modal groups (motion, stopping, non-modal). Used
 // internally by the parser to know which command to execute.
diff --git a/settings.h b/settings.h
index 04883b9..40c5cca 100644
--- a/settings.h
+++ b/settings.h
@@ -25,8 +25,8 @@
 #include <math.h>
 #include "nuts_bolts.h"
 
-#define GRBL_VERSION "0.9b"
-#define GRBL_VERSION_BUILD "20131210"
+#define GRBL_VERSION "0.9c"
+#define GRBL_VERSION_BUILD "20131231"
 
 // Version of the EEPROM data. Will be used to migrate existing data from older versions of Grbl
 // when firmware is upgraded. Always stored in byte 0 of eeprom
diff --git a/stepper.c b/stepper.c
index 128646c..a012677 100644
--- a/stepper.c
+++ b/stepper.c
@@ -34,11 +34,13 @@
 #define RAMP_CRUISE 1
 #define RAMP_DECEL 2
 
-
+// Can't have a high of a cutoff frequency. The 16-bit timer isn't as accurate as it seems.
+// There is a trade between the accuracy of the timer and the smoothness of multi-axis steps.
+// 
 #define MAX_AMASS_LEVEL 3
-#define AMASS_LEVEL1 (F_CPU/10000)
-#define AMASS_LEVEL2 (F_CPU/5000)
-#define AMASS_LEVEL3 (F_CPU/2500)
+#define AMASS_LEVEL1 (F_CPU/8000) 
+#define AMASS_LEVEL2 (F_CPU/4000)
+#define AMASS_LEVEL3 (F_CPU/2000)
 
 
 // Stores the planner block Bresenham algorithm execution data for the segments in the segment 
@@ -134,8 +136,6 @@ typedef struct {
 static st_prep_t prep;
 
 
-static void st_config_step_timer(uint32_t cycles);
-
 /*    BLOCK VELOCITY PROFILE DEFINITION 
           __________________________
          /|                        |\     _________________         ^
@@ -727,14 +727,14 @@ void st_prep_buffer()
     #ifdef ADAPTIVE_MULTI_AXIS_STEP_SMOOTHING        
       // Compute step timing and multi-axis smoothing level.
       // NOTE: Only one prescalar is required with AMASS enabled.
-      if (cycles > AMASS_LEVEL1) { 
-        if (cycles > AMASS_LEVEL2) { 
-          if (cycles > AMASS_LEVEL3) { prep_segment->amass_level = 3; }
-          else { prep_segment->amass_level = 2; }    
-        } else { prep_segment->amass_level = 1; }
+      if (cycles < AMASS_LEVEL1) { prep_segment->amass_level = 0; }
+      else {
+        if (cycles < AMASS_LEVEL2) { prep_segment->amass_level = 1; }
+        else if (cycles < AMASS_LEVEL3) { prep_segment->amass_level = 2; }
+        else { prep_segment->amass_level = 3; }    
         cycles >>= prep_segment->amass_level; 
         prep_segment->n_step <<= prep_segment->amass_level;
-      } else { prep_segment->amass_level = 0; }
+      }
       if (cycles < (1UL << 16)) { prep_segment->cycles_per_tick = cycles; } // < 65536 (4.1ms @ 16MHz)
       else { prep_segment->cycles_per_tick = 0xffff; } // Just set the slowest speed possible.
     #else 
@@ -749,7 +749,7 @@ void st_prep_buffer()
         prep_segment->prescaler = 3; // prescaler: 64
         if (cycles < (1UL << 22)) { // < 4194304 (262ms@16MHz)
           prep_segment->cycles_per_tick =  cycles >> 6;
-        } else { // Just set the slowest speed possible.
+        } else { // Just set the slowest speed possible. (Around 4 step/sec.)
           prep_segment->cycles_per_tick = 0xffff;
         }
       }
@@ -778,7 +778,7 @@ void st_prep_buffer()
       
         if (sys.state == STATE_HOLD) { 
           if (prep.current_speed == 0.0) { 
-  // TODO: Check if the segment buffer gets initialized correctly.
+// TODO: Check if the segment buffer gets initialized correctly.
             plan_cycle_reinitialize();
             sys.state = STATE_QUEUED; 
           }