PLL_XCLK_CNTL
uint8 ioValue = Mach64_GetPLLReg(PLL_XCLK_CNTL);
tmp = Mach64_GetPLLReg(PLL_XCLK_CNTL);
Mach64_SetPLLReg(PLL_XCLK_CNTL, tmp | (0x10 << clkNum));
Mach64_SetPLLReg(PLL_XCLK_CNTL, tmp & ~(0x10 << clkNum));