Osprey uses Vr4181, which is a different chip from vr4181a.

Yeah I didn't notice the A on there. We are looking into the possibility of
using the A in our board. Part of the problem is that the A only comes in
BGA and we don't like dealing with that.

Interesting.  I was trying to get RT-Linux working at one time
but aborted that effort in the middle.

Getting RTAI working wasn't easy. Took over a week and it was supposedly
already "ported." One of these days I really must find the time to check in
my changes to that project. It works very well and is quite stable. I think
46 us worst-case interrupt response off one of the VR4181's interrupts from
an external source is very good.

Steve