Jochen wrote:

> >> 	The later NVAX systems used the MS690 modules and a
> >>	slightly revised backplane. The later VAX 4000-300 systems
> >> 	also had that same backplane. The part number is 54-19354-01,
> > I have a BA440 with a 54-19353-01 backplane. Can I put a MV 4000-400
> > CPU in it? I have a -300 and I can get a -400 CPU + 64 MB RAM...
	>Ups! Sorry. I have a 50-19353-01. Antonio, are you sure that the
Number
	>starts with "54-"?

	The manual I looked in quotes 54-19354-01.
	I never did fully understand all the intricacies
	of 2-5-2 part numbers but I think
	that 50-xxxxx-xx is the number for the PCB
	(circuit board) and 54-xxxxx-xx is the number
	for the same PCB once it has had a bunch of
	components mounted on it. Or it could be the
	other way around :-)

	Now there is no reason that the bits after 50- or
	54- have to match, but in my experience they
	generally do.

	So it looks to me like you have an earlier VAX 4000-300
	which has the 32-bit backplane rather than the 64-bit
	one required by all the later processors.

	The other way to determine what you have is to look
	at the system serial number. But I no longer
	have the "cut-off" numbers beyond which you
	can be sure you have the newer style backplane.
	I believe that I posted those numbers a number
	of years ago, so if deja were running you
	could have a hunt ... but it isn't :-(

	Antonio