Originally Posted by Tony
Think of it this way:
The chipset has 4 working ranges for speed, these are dictated by the multiplier set for the clock frequency of the chipset.
The Clock generator for the CPU etc has the same 4 working ranges, these are dictated by the BSEL pins on the CPU..IE the strap it sets.
The ram speed ratios are dictated by the chipset dependant on what chipset multiplier has been set for its internal frequency.
Now: the chipset has a max clock just like a cpu does, as you ramp up the clock frequency you may have to lower the mutiplier...you do this by going to a higher chipset strap..IE going from 800 to 1066 etc.
The Clockgenerator has the same issues, its internal PLL has a max working frequency, when you change the BSEL strap on the CPU you actually reset the PLL but initiate the clock at a higher base setting...so, if you moved from 800 to 1066 the FSB working range may be the same 100fsb you have available going from 200fsb to 300 but the base clock the clockgenerator starts at has moved from 200 to 267 so instead of maxing at 300fsb you now max at 367fsb.
finally the lower the strap set the more aggressive the internal latency on the chipset, this means the ram is faster but may not do the tight timings or may not clock as high.Ram ratios are dictated by dividers preset within the chipset per the strap it is set to....1:1 at 800 strap will not be 1:1 on the 1066 strap etc.
Hope this helps