Could someone explain FSB straps to me?

hi all,

I'd like to know what the difference between fsb straps is....even if you run the ram at the same speeds between straps what are the benefits of running ram at say......1066 using 400mhz strap - or 1066 using the 266mhz fsb strap?

I've messed with them since i started to OC about 2 years ago - but never really knew what they meant!

I've heard people say "tighted up the strap" or "that's a loose strap tighted those up"

What does it mean - tighted - loosen - with the fsb strap??

thanks