FreeBSD supports the "SysMouse" protocol which must be
specified when the moused daemon is running in versions 2.2.1
or later.
FreeBSD versions 2.2.5 or earlier do not support extended PS/2
mouse protocols ("xxxPS/2").
Always specify the "PS/2" protocol for any PS/2 mouse
in these versions regardless of the brand of the mouse.
FreeBSD versions 2.2.6 or later include the kernel-level
support for these mice.
Specify the "PS/2" or "Auto" protocol and
the X server will automatically make use of the kernel-level support.
In fact, you may always specify "Auto" to any mouse in these
versions unless the mouse is an old serial model which doesn't support PnP.