CAS Latency question

I have sticks of DDR2 PC5300 running on a 533 bus. On a 667 bus the latency
is published ot ne 5 but CPU ID states 4 @ 533. Have I got this correct ?
Looking at replacing ram per prior post. I had a higher Windows EXP. score
with pc4200 ram running at a 4 latency yes there is a cost advantage at the
moment for the 5300 ram / 667 bus / 5 latency. I'd like ot put in the 5300
and let the MB step it down to 533 @ 4.