Lpc2000

I just looked at the cycle timing specs of the ARM7TDMI-S and I must
say.. I don't understand it.
I made the following test:
- Programm is running in flash
- MAM is at max speed
- PLL is set to M = 5 and P = 2 @ 12 MHz Foc -> 60 MHz cclk
- Pogramm is 100% THUMB, assembler coded
- r2 holds IO1SET, r0 holds IO1CLR, r1 holds the bit position
- I am scoping the the following loop:

loop:
   str r1, [r0]
   str r1, [r2]
   b loop

The scope shows a frequency of about 1,666 MHz at the output pin. With
some testing, eg doubling one of the str, i figgured out that the b is
nearly done in 1 cclk cycle. But the 1,666 MHz will mean that one str
takes about 18 cclk cycles( also tested with PLL off, same result the
Freq is exactly 1/5).
Now there are 2 things that I don't understand:
1. 18 cycles lookes very long to me. Can that be?
1. How can I calculate the exact value of the instructions?

regards

Thomas