I pulled this From Chris SI's site.
AMD HAS CONFIRMED that it will not include support for PCI Express for future Athlon XP processors.
One thing to keep in mind is that AMD only produces chipsets to "seed the market". It has been some time since AMD made a chipset for the Athlon XP or MP. They are not in the chipset business.
When the original Athlon came out AMD made a chipset for it so companies could make motherboards. Once VIA, nVidia and others were in the market AMD backed out, as planned. Right now they make chipsets for the Athlon 64 and Opteron. Once 3rd party chipsets become prevalent they will phase out the AMD chipsets.
As to support for PCI Express with the Athlon XP, MP or Duron. Why would they bother? These chips are being phased out in favour of the Athlon 64, Opteron and Sempron. Why design a new chipset and motherboard series for an end of line chip?
Intel on the otherhand has a major business making chipsets and licensing others to do so AND the Pentium 4 is the current chip. It's replacement is not yet on the market or even clearly defined to the public. So Intel
must support PCI-Express on the Pentium 4, Xeon and Celeron lines.