Putting two memory controllers on a 780?

[Dave Martindale]

Well, the MS780-E isn't really two memory controllers, and it isn't really
one.  It's two control boards which share a common SBI interface board.
So there are two copies of some registers, and only one of another.
They are sufficiently different that the 4.1/4.2 memory controller code
as distributed will not handle reporting of errors from the new controller
correctly, even though the autoconfig stuff has been changed to recognize
the new controller in 4.2BSD.