Recognize Xbox 360 Jasper (Part II)

If you get a Jasper it's not guaranteed that you'll get a 150W power supply, Microsoft still has a lot of Falcons and Falcon-parts in its distribution system so some Jaspers have been sighted with 175W power supplies. If you end up with a 175W unit it's not a big deal, it's going to be slightly less efficient than the 150W unit and your system may end up drawing an extra few watts but it's not a big deal at all - you'll still be far cooler/more power efficient than a Falcon (and possibly be red-ring-free).
To prevent an under powered power supply from being used in the wrong Xbox, Microsoft keyed each of the three Xbox 360 generations differently. The picture below explains it all:



If you see one flat bar on top and a square peg in the middle of the power connector on the console itself you've got a 1st generation Xenon or Zephyr board, these machines use 90nm CPUs and GPUs. If you've just got a flat bar on top with no square peg in the middle, you've got a 2nd generation Opus or Falcon board, these things use 65nm CPUs and 80nm GPUs. Finally if you've got a flat bar split in two on top with no square peg you've got a Jasper, that's a board with a 65nm CPU and a 65nm GPU.

Source: www.anandtech.com