Not within FCP, unfortunately. FCP is still built on a 32 bit architecture.
The dramatic speed increase and power of 64 bit processing is evident in Compressor- a 2 pass mpeg2 encoding renders faster than real time. That speed bump hasn't been brought over to FCP yet... Though background apps run more smoothly (so you can have Compressor crunching your stuff on 6 cores while you are editing in FCP).
To increase the overall speed, faster drives, faster interfaces, would come in handy..
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