Subject: Re: MicroVAX I
To: None <port-vax@NetBSD.ORG>
From: Roger Ivie <>
List: port-vax
Date: 03/25/1996 11:41:43
> Unless I'm totally confused, it's a very plain Q-bus, same stuff
> as in the MVII. The two differences I seem to remember is how the
> memory is connected, and the fact that it's a different chip set.
> Slow like hell, and you emulate a lot of the more advanced instructions.

The mind-bogglingly important thing about the MicroVAX I is that since it is
a pure Qbus machine, you a) can't have more than 4MB of memory and
b) don't have a scatter/gather map between Qbus DMA space and memory.

VMS device drivers deal with the MicroVAX I's lack of a scatter/gather map by
allocating a physically contiguous buffer into which DM is performed and
then spoon-feeding the data to the user's buffer.

Since the stock NetBSD Qbus drivers all expect there to be a scatter/gather map,
they'll need some work to run with a MicroVAX I.

Roger Ivie