nVidia knew ahead of time that athlon would be ramped up to 200 fsb when the barton was released, so they desgned their chipset to run at 400 when necessary. Unlike VIA that constantly "updates" a new chipset, making consumers buy a newer motherboard to support upcoming processors. nVidia offers 2 lines of products supporting the best of the Athlon cpus...
VIA...
KX133 (slot A)
KT133
KT133A
KM133
KT266
KT266A
KT333
KT400
soon to be KT400A
nViidia......
Nforce IGP/SSP (came out same time)
Nforce 2 IGP/SSP (SSP came out 1 1/2 earlier)