> The 3c90x documentation, however, is not available, and at this
> point the 3Com person in charge of handing this stuff out thinks
> the engineers aren't going to have it ready for her until the end
> of the year.

I just got my package from 3Com yesterday -- the TR manuals for the
3c509 and the 3c590.  It sounds like we are going to be attacking
this same problem, so please keep in touch!  I will certainly pass
along anything I manage to get worked out.

> The reason that this is important is that the 3c900
> uses a somewhat different (and faster) method of bus-master DMA
> transfers, if you run it in DMA mode. I also hear that the next
> stepping of the 3c900 chip will not support PIO mode any more,

I heard this as a maybe -- that is that the Rev B of the 3c900 will
drop the PIO mode which provides backwards compatibility with the
3c590.  I also asked if the 3c590 is going to be dropped as a product
and got a tentative no.

There is a kindof unpleasant gotcha in all of this.  The Rev A of
the 3c900 has some kind of bug doing receive DMA at 10 mbps, so you
really need to run it in PIO mode if you are running at that speed
(as I will be, I don't have a 3c905).  The Rev B may drop the PIO
mode, so they had better fix the receive DMA bug.

In spite of this, both the nice lady at 3com (Terry) and the linux
network driver guru (Donald Becker) say that the 3c900 is a better
choice than the 3c590.  ( If they didn't say that I would already
have traded mine in ... )

> which means we will have to use a different driver for it.  (The
> Linux driver is extremely well documented, so I can give that a
> close reading and see how much it gives me to go on.)

I have been looking at it as well.  Unfortunately projects here at
work are going to demand most of my time over the next few weeks,
so I won't have a chance to work on it, so my 3c900 sits idle and
I will run my SMC ISA bus card.  Or is there a quick patch to the
3c590 driver that will just let me run my 3c900 is PIO mode or some
such?  I got the impression reading this list that people were doing
that, but didn't see any code in NetBSD-current on netbsd.org.
I am actually running 1.2 on my machine.

> Of course, I don't know anything about PCI DMA, so now there's all
> that to learn....

Yep, me too.  Donald's linux drivers will be a big help.

	Tom

-- 
	Tom Trebisky			Steward Observatory
	ttrebisky@as.arizona.edu	University of Arizona
	(520) 621-5135			Tucson, Arizona 85721