see http://mbed.org/users/no2chem/notebook/mbed-clock-control--benchmarks/

Dependencies:   mbed

Revision:
0:b5d3bd64d2dc
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/ClockControl/ClockControl.h	Sun Jan 24 15:46:26 2010 +0000
@@ -0,0 +1,14 @@
+/* mbed PowerControl Library
+  * Copyright (c) 2010 Michael Wei
+  */ 
+  
+//shouldn't have to include, but fixes weird problems with defines
+#include "LPC1768/LPC17xx.h"
+
+#ifndef MBED_CLOCKCONTROL_H 
+#define MBED_CLOCKCONTROL_H 
+
+unsigned int setSystemFrequency(unsigned char clkDivider, unsigned char clkSrc, unsigned short M, unsigned char N);
+void setPLL0Frequency(unsigned char clkSrc, unsigned short M, unsigned char N);
+void setPLL1Frequency(unsigned char clkSrc, unsigned short M, unsigned char N);
+#endif
\ No newline at end of file