multipliers / dividers

[CTho9305]

how do they REALLY work? I can see how to turn a 100mhz pulse into a 50mhz... you just skip every other. but how do you get a 66 mhz pulse out of 100? you can't skip 1/3 the pulses b/c then you will have a 100mhz rate with breaks every 2 cycles. AND... how does the motherboard's pll (or anything) take the base 14.3mhz (i think) output from the crystal and get 33.3/100/66/etc?

 

[DeeK]

Do a web search for "Phase locked loops". PLLs allow a clock to be multiplied/divided by any integer. To get 66MHz from 100MHz, use a multiplier of 2 and a divider of 3. A quick search gives this page for starters.

 

[CTho9305]

good read, thanks