Path: utzoo!mnetor!uunet!seismo!sundc!pitstop!sun!decwrl!pyramid!voder!apple!korn
From: korn@apple.UUCP (Peter "Arrgh" Korn)
Newsgroups: comp.sys.mac
Subject: Re: EtherTalk vs. LocalTalk on Mac II
Message-ID: <7352@apple.UUCP>
Date: 8 Feb 88 03:26:34 GMT
References: <9414@steinmetz.steinmetz.UUCP> <11540122@hpsmtc1.HP.COM> <2584@emory.uucp>
Reply-To: korn@apple.UUCP (Peter "Arrgh" Korn)
Organization: Apple Computer Inc., Cupertino, USA
Lines: 73
Disclaimer:  I wasn't hired to give Apple's opinions


In article <2584@emory.uucp> phssra@emory.UUCP (Scott R. Anderson) wrote:
>In article <11540122@hpsmtc1.HP.COM> dlw@hpsmtc1.HP.COM (David Williams) wrote:

>>Hmmmm, I think what she means is that you can only have Ethertalk or LocalTalk
>>active at any one time. The serial ports still function while ET is active, 
>>but they can not run Localtalk at the same time as ET is running.
>
>This is an unfortunate limitation!  What if I want to print graphics or text
>from my UNIX login screen to my LocalTalked LaserWriter?  Or receive mail over
>LocalTalk while logged in to UNIX?  Or any number of other concurrent uses one
>can imagine!

It is, and then again, it isn't a limitaiton.  The first question to ask is,
how are you connected to your UNIX login screen?  Are you running A/UX and
have a macintosh process running under A/UX that you want to print from?
Are you running MacTerminal (or some other like program) that you've connected
via a serial line to a UNIX host?  via an AppleTalk line to a UNIX host?
via an EtherNet TCP/IP line to a UNIX host?

Lets assume your under A/UX.  Then you will *need* to get a card (AST currently
makes one) that puts LocalTalk on the NuBus to do LocalTalk, because the
way it's implemented under the Mac OS (and on the Mac II board) is via 
interrupts; and this would flail A/UX alive (interrupting the kernel simply
isn't done you know).  Alternately you could have an EtherTalk card (ours
or Knetics or someone elses), and talk AppleTalk protocalls via that card.
Then, somewhere on your network, you will have an EtherTalk to LocalTalk
bridge (such as the one made by Knetics), and on the LocalTalk net (or
subnet, if you will), you will put your LaserWriters and Mac Plus, Mac SE,
etc. machines.

Alternately, let's say that you are running under the Mac OS, and have a
macintosh program that allows you to connect to a host machine (again, like
MacTerminal).  Then, your connection to that host is via that program; no
LocalTalk necessarily involved.  If you have a program that embeds your
connection in AppleTalk packets, (Knetics has some stuff to do this, as well
as one or two other companies I believe), then again you are still using
that LocalTalk connection on the back of your Mac.

Lastly, you could be talking TCP/IP on a NuBus board to your UNIX host
(again, under the Mac OS), and talking LocalTalk out of the back of your
MacII.  And with a board that does both TCP/IP and EtherTalk (AppleTalk
packets on Ethernet cabling) at the same time, you could do it all that
way.

If you want a UNIX box to print on a LaserWriter, that's fine.  That
UNIX box has to either be connected to that LaserWriter via the serial
connection (which will effectively force all connections to that LaserWriter
to go through the UNIX box; the LaserWriter cannot take jobs simultaneously
from it's serial and it's LocalTalk connections), or that UNIX box can
somehow be on LocalTalk or EtherNet talking AppleTalk protocalls like
everyone else.

Another neat approach would be to set up your UNIX box on EtherNet talking
AppleTalk protocalls as an AFP file server (basically AppleShare with a
UNIX-based host).  Further, you could have that UNIX box also be serving
the LaserWriter that it's connected to serially (it broadcasts packets over
EtherNet in AppleTalk protocall saying that it's a LaserShare-type server,
and it can take LaserWriter jobs; which it will then spool to the LaserWriter
it's connected to serially).  If I'm not mistaken, several Universities
have done the former; I'm not sure if any of them have their AFP servers
also acting as AppleTalk print spoolers; but again, there is nothing in the
protocall to prevent this.


The limitation is simply this:  you cannot have more than one active physical
AppleTalk connection under the Mac OS (and there are even not-so-kosher ways
of getting around this; but don't do it!).  There is nothing to stop you from 
having other connections of other sorts at the same time.


Hope this clears things up some...

Peter