http://mail-index.netbsd.org/port-alpha/2000/08/18/0003.html

To follow up on this old thread, I decided to dig some more into this.
I noticed that a gdb backtrace showed a NULL getting passed to
tga_intr, so I put a ddb breakpoint in that function to see when this
happened. Which it didn't. An added assert at the start of that
function gave nothing either (except the usual memory management
traps). What does the trick is a printf in that function. This leads
me to believe that the problem is timing related.

How can I debug this further?

A related problem is with the Xserver itself. It seems to behave badly
when moving windows, best described by the image at
http://www.pdc.kth.se/~joda/broken-xterm.gif

This is the result of moving the xterm window down; moving it
horizontally doesn't seem to have this effect.

/Johan