Hi James,
Officially we’re recommending a dual G4/1.25 GHz or faster for use with Tiger and Mac OS X 10.4. The change in requirements is related to our complete switch to the Apple uncompressed codecs. They require something faster than the previously recommended dual G4/800 MHz and the your dual G4/1 GHz might be OK but ours died a while ago so we couldn’t verify that model. Chances are that it will work OK but it will be at the low end of what might work and so that’s why we posted conservative requirements of a dual G4/1.25 GHz or faster.
If you continue to work with Panther and Final Cut Pro HD v4.5, then your Mac should be fine as this configuration only requires a dual G4/800 MHz.
Regards,
Luke Maslen
Blackmagic Design