STM32F407 discovery board core clock setting

Hello,

I am experimenting with the STM32F407 discovery board. In order to run the sine.uvproj to get correct timing information, I tried to change the program settings for the correct hardware Xtal frequency which is 8 MHz instead of 25 MHz in the program supplied. Here are what I did:

1) In file "stm32f4xx.h"
change
#define HSE_VALUE ((uint32_t)25000000)
to
#define HSE_VALUE ((uint32_t)8000000)

2) In file "system_stm32f4xx.c
Change
#define PLL_M 25
to
#define PLL_M 8

3) In file RTX_Conf_STM32F4.c
Change #define OS_CLOCK 53760000
to #define OS_CLOCK 168000000

4) Set the "Core Clock" to 168000000 in the Trace Tab of Cortex-M Target Driver Setup

I ran the program, the waveform in the Analyzer was completely srewed up. I was able to get a nice sine wave previously (the frequency of the waveform is incorrect due to the CPU clock setting) but never the less, I got a sine wave. So somthing else in the program need to be changed and I can not figure out where and what.

Please help.

Thanks

Jim