The image below shows a regular Jasper PSU and right below the PSU (which is about 1/4th smaller) from an Arcade Jasper-based Xbox360 with 512MB internal MU manufactured in May 2009.
The new PSU is still 150W, so no change there.
To quote legueux, roughly translated from French:
nono85 us back information on the power supply for Xbox 360 which has seen its size reduced by a quarter compared to blocks distributed so far.
The block at the top of the picture corresponding to a distributed power 150w with Jasper in March 2009.
The block at the bottom of the picture corresponds to a 150w power supply after a pack containing the new Arcarde Jasper revision in May 2009 with 512MB of onboard memory.
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