Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!cs.utexas.edu!uunet!mcvax!ukc!icdoc!qmc-cs!liam From: liam@cs.qmc.ac.uk (William Roberts) Newsgroups: comp.unix.aux Subject: Re: Printing to AT / AT Coprocessing Card? Summary: Yes, you have to buy extra hardware Message-ID: <1147@sequent.cs.qmc.ac.uk> Date: 3 Jul 89 17:38:18 GMT References: <4170@uhccux.uhcc.hawaii.edu> Reply-To: liam@cs.qmc.ac.uk (William Roberts) Organization: Computer Science Dept, Queen Mary College, University of London, UK. Lines: 38 Expires: Sender: Followup-To: Distribution: Keywords: In article <4170@uhccux.uhcc.hawaii.edu> david@uhccux.uhcc.hawaii.edu (David Lassner) writes: >Page 10-1 of the A/UX 1.1 Network System Administration reference >says "Because of the high processing requirements of both AppleTalk >and the A/UX multitasking OS, AppleTalk under A/UX requires a coprocessing >card. ... >Is this for real? Do we really need a card to print to an AppleTalked >LaserWriter Yes, it's for real. The problems is to do with interrupt service times and the very feeble hardware provided for the LocalTalk interface. Basically that thing has a three byte buffer inside it, so you have to pull those bytes out very, very quickly if you don't want to lose packets. I did hear something about AT&T requiring a minimum interrupt service time from anything to be called "UNIX" and it being very hard to meet this with the Mac II hardware. They could use a newer version of the chip (bigger buffer), but the current trend at Apple seems to be using add-in hardware for comms. In particular, they are keen on co-processor cards, i.e. where you make the card do some of the work and so off-load processing effort from the Mac II. > and if so, who makes them? The manual entry you quoted says it all: > Contact your Apple representative for a list of cards that are >available from various vendors." I admit it is rather bizarre (it can talk LocalTalk when it's a MacOS machine, what happened under A/UX?) but there does seem to be a reason for it. At least your Apple representative is likely to tell you ALL of the vendors who make such cards :-) -- William Roberts ARPA: liam@cs.qmc.ac.uk Queen Mary College UUCP: liam@qmc-cs.UUCP AppleLink: UK0087 190 Mile End Road Tel: 01-975 5250 LONDON, E1 4NS, UK Fax: 01-981 7517