Degraded X performance in 7.0

[george+freebsd at m5p.com]

Between FreeBSD 6.2 and FreeBSD 7.0, something has happened with
performance.  Using a generic 6.2 kernel and the X server which
shipped with it, and mplayer built with the defaults from ports,
I would play a movie from an NFS-mounted disk, with mplayer using
roughly 30% of the CPU time and xorg less than 5%.  On the very same
hardware upgraded to a generic 7.0 kernel and the X server which
shipped with it, and mplayer built with the defaults from ports,
playing the same movie from the same NFS-mounted disk, mplayer
still takes roughly 30% of the CPU, but xorg is taking 35-40% of
the CPU!  The quality of the playback is noticeably rough.  What
should I be looking for?  The diff between an old Xorg.0.log and
a new one is pretty massive.  I have an ATI Technologies Inc Rage
XL AGP 2X rev 39, Mem @ 0xce000000/24, 0xcfeff000/12, I/O @ 0x8800/8,
BIOS @ 0xcfec0000/17 according to the log.

Thanks for any assistance you can give me!    -- George Mitchell