Does anyone know what, if any, differences there are between the MV3500 and
MV3800 that are visible to system software (other than cpu speed, of course)?

A vaguely recall that some KA6nn motherboards have DSSI disk and ethernet
interfaces on them, but that the MV3800 (KA655??) doesn't. If that is the
case, it shouldn't take much more than the changes for the MV3500 (KA650).
(KA650 support isn't there now, but hopefully will be in not too long)

Well, if anyone else can fill in the details on it, please do so, rick