The hammer (supposedly) comes out in a year and will use up to 3 hypertransports (starting probably with one).
Barton will likely also use hypertransport. It should come out before the hammer (late summer or fall).
Keep in mind that Barton (AMD) and Hammer will have many other improvements in speed in addition to hypertransport technology.
The reason (Sledge)Hammer has up to 3 hypertransport links is because it can be utilized in a mult-processor board exceeding 2 CPU's (up to 4 total). The first two are used to interface with the other two processors forming the corner of a square, and the final HT link ties the processor to the I/O bus. Clawhammer will undoubtedly not use all HT links as it will be targeted to the single processor market. Let's not forget too that Hammer essentially has two cores, and SMT will likely be available as in the Northwood. Clawhammer chipsets will use Hypertransport with a bus speed of 800MHz and a total bandwidth of 6.4 Giga Byte/s. Three times that of the current 266 MHz EV6 bus.
Barton is the same core as Thoroughbred, but will use SOI wafers. I doubt the motherboard manufacturers will change their chipsets (and their associated bus) if the Thoroughbred is fully compatible with existing V-link and multi I/O technology. They might adapt hypertransport, but unless the benefits are great I wouldn't hold my breath.
