Compiler/TMS320F28035: Simple loop delay does not match with CPU clock

Tool/software: TI C/C++ Compiler

Hi,

I want to implement a loop delay using simple delay function like this

void DelayUs(unsigned long usec)
{
usec = usec * (Instruction_Multiplier);  //3 to 4  cycles
while (usec--)  // two cycles
__asm(" NOP"); //one cycles
}

My 28035 clock is 60Mhz and instruction time is 0.016666 micro seconds. So each decrement will take 3 cycles approx. 

Considering clock speed, I should have approx 166 decrements in one microsecond. 

While(usec--);__asm(" NOP") will take 3 cycle for each decrement. So Ideally I should use 166/3 = 55 as Instruction_Multiplier in the code.

But when I tested the code, it was 10 times slower. I had to use 5 as Instruction_Multiplier, then only I was able to match the delay.

Could I be using a slower clock?