Subject: Re: port-next68k
To: Darrin B. Jewell <jewell@MIT.EDU>
From: Soren S. Jorvang <>
List: port-next68k
Date: 07/08/1998 20:26:41
On Wed, Jul 08, 1998 at 12:00:12PM -0400, Darrin B. Jewell wrote:
> "Soren S. Jorvang" <soren@t.DK> writes:
> > The ethernet controller in my machine (Turbo Color)
> > is an AMD 7996. How compatible with the Fujitsu chip
> > it is, I don't know - as far as I can tell, AMD only
> > has a electrical specs data sheet for it available on
> > their web site.
> This is a common misconception because you can see the chip
> on the board.  I'm 95% certain that what you see is not
> an entire ethernet chip, it's just the wire that flips the bits
> on the wire.  I'm pretty sure my machine has the chip labelled
> 7996 as well, but I'd have to take a look again to be sure.

You're right. The AMD spec sheet does say 'transceiver'. Erm.. :-)

I can't find anything resembling a 8795 anywhere, but the
ethernet controller could well be on the underside of the
board, where I have not looked.

> > At least it is not an entirely different chip.
> > The MAC address can be read, and some of the register
> > contents seem to correlate with the *reg.h constants.
> The MAC address is read from ROM, not the ethernet chip.

What I meant was that the MAC address can be read from
the chip after being reset registers. Most likely this
is put there by the PROM loader.

Is a reset supposed to clear the on-chip MAC address?

> > I have tried frobbing the chip some, but with
> > no success. I can't find any 8795 documentation on
> > the Fujitsu site, either.
> There isn't really much available.  It's the same chip used
> on an IBM RT Ungermann-Bass ethernet board, but it's hooked
> up using NeXT-special DMA interface.    The main reason
> this port wasn't trivial enough to have been done years ago
> is the lack of documentation.

Okay. Do you have any suggestions for things I could try?

I got someone from Fujitsu Microelectronics to search
their archives for MB8795 and MB502 programming
manuals. I'll let you know if he comes up with anything.

Of course, that still leaves the significant possibility of
NeXT-specific differences.