ubuntu 12.10 on macbook 1,1 - trackpad slow

hi,

I've just installed ubuntu 12.10 on my macbook 1,1 (april 2006).
everything seems to be fine except the trackpad.
the response is very slow and inaccurate, however both the left and the right click works fine.

do you think it's a driver problem?
or unity is too heavy for such an old cpu?

thanks!