Here's another question ... how many x86 mobos support 4 GB RAM? Your BX/i840/AMD760 type boards support 4 slots. Currently DDR only comes in 256MB sticks though 512MB sticks will be available shortly (actually, might be already though Crucial's website doesn't list them as available and I know Fry's doesn't have them yet though they will "real soon now").
So at the moment building or buying an Athlon-based server restricts you to 1GB, with 2GB being posible soon.
Crucial does have 1 GB SDRAM ECC PC133 sticks for $200 so yeah, OK, you can build up to 4 GB. Supermicro offers SMP mobos that support this and run with modern socket-based PIIIs but the chipset's a non-Intel one called the ServerWorks ServerSet III LE. Sounds more impressive than "GX", doesn't it? :)
So I guess at the moment going for this much RAM in an SMP configuration, at least, means PIII.
(I'm intentionally ignoring RDRAM solutions and P4 solutions)
