Hi!

>Having more than 16MB or RAM definitely helps things out though,
>esp. under NetBSD (as opposed to SunOS).

Donīt talk nonsense!
SunOS makes GREAT use of every Meg!
IMHO, a 3/260 can really make use of 64MB and a 3/470
can really make use of 128MB.
NetBSD without UVM does not make ANY use of more memory
as long as the current configuration does not need to
page, which is undoubtly true for ALMOST everyone of
us, who still runs a Sun3.

With UVM, things start to change, but i BET, SunOS is
still much faster in most things. And makes better use
of the resources, especially main memory.

There is a known effect called PMAP-thrashing, which
starts to occur at 64MB on SunOS 4.1.1, but can be
patched with "adb". I donīt know, if the sun3x
architecture does have this effect too, because it
uses another type of MMU.

>Note that I've had no end of trouble with a system running four 32MB
>boards in a 3/280 under SunOS-4 -- there were many strange core dumps
>and unexplainable system crashes.

I run one 3/260 with four 8MB boards and these beasts
suck a lot of power from the power supply. But it works
quite good. I have 7 8MB boards and these four are the
only ones, which run stable in this four board configuration.
The other boards seem to have become flaky, they show
random ECC errors after a couple of days and the machine
crashes after a week or so, if i use them.

I have one 32MB board, which works in my 3/470. The
machine crashes every week with a memory fault.

Iīd say, the memory boards have become old and flaky.

One hint: Search for the bus terminators! These are
16pin yellow chips near the midle VME connector.
You must have one on the rightmost and one on the
leftmost (usually the CPU) board and you must not
have terminators on boards in between.
On a "normal" configuration, the board in slot 1
(CPU) and the board in slot 6 (first memory board)
should have these terminators. More memory boards
in slot 5,4,3 (you should leave slot 2 empty and
do NOT put a placeholder into it) must not have
a termination resistor pack.

And as usual: Have fun!

Peter