clock frequency


I wanted to test the speed of an algorithm I’ve written for my RC3700. For that I changed one pin after each calculation from low to high and measured this time. Then I was surprised when I saw that for toggling one pin without calculation the Rabbit needs 2.5us. I supposed that the Rabbit also could toggle his pin with clock Frequency of 22.1MHz. Is this wrong? Or do I have to use another command to switch the pins?
This is like I’ve done it:

#define SPI_direction PBDDR
#define SPI_direction_shadow &PBDDRShadow
#define SPI_port PBDR
#define SPI_shadow &PBDRShadow
#define SPI_SLCK  0

#memmap xmem

nodebug void main()
     BitWrPortI( SPI_direction, SPI_direction_shadow, 1, SPI_SLCK);
          BitWrPortI(SPI_port, SPI_shadow, 0, SPI_SLCK);
          BitWrPortI(SPI_port, SPI_shadow, 1, SPI_SLCK);

Thanks for your help