Socket 423 is being phased out. Socket 478 is the newer version, but is no faster than socket 423 until the northwood chip arrives in a month or two. Socket 423 stops at 2 or 2.2 megahurtz, with no upgradability beyond. TH7 is the board for 423, TH7-II is for socket 478. Both are for rdram. If you overclock, I would go with the abit board. There are good system closeout deals on socket 423. And no, socket 423 and 478 are not interchangable. Socket 478 speeds range from 1.5-1.9, possibly higher.