What chip set do you have? The 533 MHz system runs a 133MHz memory bus that
becomes 266MHz Dual Data Rate, that becomes 533MHz Dual Channel Dual Data
Rate. Hence a 400MHz FSB Pentium 4 board is rare unless it's very old.
They aren't all that rare! The Pentium 4 first shipped with a 400MT/s
bus speed on the 20th of Nov, 2000. The very first 533MT/s bus speed
P4 chips didn't ship until May 6, 2002. That's a good year and a half
where 400MT/s bus speed boards were all that was out there.
Also, I'm not really sure what you're getting on about with that
memory bus. The memory bus and processor bus most definitely do not
need to be synchronous in the vast majority of P4 chipsets (it's a
good idea, but not required). What's more, while one could argue one
either side of the argument that a Double Data Rate memory bus running
at 133MHz was a "266MHz" bus (I would say 'no', since your clock speed
is still 133MHz, it's only your data rate that is doubling and it is
not measured in Hz), it's most definitely false to say that
dual-channel memory bus double things again. A dual-channel memory
bus running at 200MHz is still running at 200MHz. It's twice as wide,
but the clock isn't changing.
