It was pointed out to me by Chuck Cranor that the Sun3 DVMA space
for external VME access (slave mode) is only 1MB, not 16MB.  My
confusion came from the fact that the on-board DVMA devices are
mapped to the last 16MB of VA space, whereas external VME access
is mapped to the last 1MB of VA space.  Understandable confusion.

Anyway this explains why the standalone disk boot program failed
on the 3/260 with: "scsi: dvma bus error" (mind goes "click").
After I fixed the standalone dvma support, it works!

The sun3 port now has fully working boot programs.

Gordon