Ultra 5 "reproducible" XF86_Mach64 lockups

[Tibor Simko <tibor.simko@cern.ch>]

Hello

I obtain repetitive lockups of Ultra 5 under X11, Sun Type 5 keyboard;
kernel 2.2.15, synced with current potato.

The lockup typically occurs within 1 minute of intensive X input.  To
"reproduce" it I use xdvi and emacs and rapidly click with mouse here
and there, change scales, skip through pages, reread file, etc.  The
lockup happens independently of the window manager (tested E, sawmill,
fvwm).

When the lockup happens both the mouse and keyboard are unusable.
Machine respond to network connections and top shows that XF86_Mach64
is working hard.  But I have not succeeded to kill X, nor to reboot
over the network connection: after such attempts the connection itself
is frozen.  The only apparent solution is to cut the power off.

I wonder whether anyone observes the same thing.  What is the best
method for further diagnosis?

cheers
-- 
TS