when the hard disk is idle but spinning, and just before shutting down.
on SWCODEC targets with > 8MB RAM the playback engine will try to
refill the buffer if it is less than 75% full while the disk is spinning
(temporarily disabled on the nano)
git-svn-id: svn://svn.rockbox.org/rockbox/trunk@11451 a1c6a512-1295-4272-9138-f99709370657
