I think all Intel CPUs since the appearing of the Core 2 Duo mobile line are 64bit capable. Only a few Cellys (from the Celeron D line), the Pentium M and the Core Duos are NOT 64 bit capable.

Also, this CPU is a direct descendant of the E21x0 line, which is also 64 bit enabled. The only difference on these Cellys (apart from the single core thing, of course) from the "bigger brothers" is the lack of EIST, every other tech available on the E21x0 is also present on the C4xx line.

Cheers.

Miguel