AMD CPUs Semperton140 & Pheom II x2 have 4000 Hyper Transportation (FSB). NewEgg lists its motherboards with FSB. Do the CPU's and motherboard's FSB need to match exactly? What if I ever get a motherboard that doesn't exactly match the FSB of the CPU?
Hypertransport is an advertising gimmick which has little relevence in the total performance. Simply check the "cpu support" section and select one of the newer chipsets, such as the 785, if your budget permits it. I use an older nvidia 6150 chipset for better value. I don't need too many features on the fancier boards. The board fsb doesn't need to match the cpu or memory fsb.
Hypertransport is used by Amd and just recently by intel. It reflects the transfer path between ram on the motherboard to (chipset in early Amd) and or the Cpu. In your example of 4000 this is two 2000 paths equaling 4000. An amd motherboard currently can yield up to 5200, two paths of 2600. The processor you put in will have a limit for it's memory controller as you can see by looking at different Amd cpu's. The motherboard will default to the specifications listed on the cpu although these settings can be overridden manually. I believe the limitation on Am2 boards is 2000, two paths of 1000. Amd2+ and Amd3 include the higher limits of 5200 theorectically. There aren't any Amd cpu's sold which currently reach the 5200 setting by factory specifications as of yet that I'm aware of. Intel chips control the ram memory bus and cpu clock speed by the FSB of the motherboard until just recently with their newest upcoming line.