diff --git a/avr/devices/s03/boot/boot.asm b/avr/devices/s03/boot/boot.asm
index 18e3064..cd5da71 100644
--- a/avr/devices/s03/boot/boot.asm
+++ b/avr/devices/s03/boot/boot.asm
@@ -6,7 +6,7 @@
 ; All definitions and changes should go into this file.
 ; ***************************************************************************
 
-.equ clock=20000000 ; Define the clock frequency
+.equ clock=16000000 ; Define the clock frequency
 
 .nolist
 .include "include/m644Pdef.inc" ; Define device ATmega644P
diff --git a/avr/devices/s03/main/main.asm b/avr/devices/s03/main/main.asm
index cff68c6..ace74c6 100644
--- a/avr/devices/s03/main/main.asm
+++ b/avr/devices/s03/main/main.asm
@@ -8,7 +8,7 @@
 ; ***************************************************************************
 
 ;.equ clock=1000000 ; Define the clock frequency
-.equ clock=20000000 ; Define the clock frequency
+.equ clock=16000000 ; Define the clock frequency