Path: utzoo!attcan!uunet!lll-winken!lll-ncis!helios.ee.lbl.gov!pasteur!ucbvax!agate!labrea!polya!kaufman
From: kaufman@polya.Stanford.EDU (Marc T. Kaufman)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Apple HD SC 80 does not support Asynch i/o.
Message-ID: <5958@polya.Stanford.EDU>
Date: 8 Jan 89 03:29:42 GMT
References: <11605@dartvax.Dartmouth.EDU> <271@berlin.acss.umn.edu> <27318@ucbvax.BERKELEY.EDU> <13271@cup.portal.com>
Reply-To: kaufman@polya.Stanford.EDU (Marc T. Kaufman)
Organization: Stanford University
Lines: 14

In article <13271@cup.portal.com> ts@cup.portal.com (Tim W Smith) writes:

>Another thing to watch out for is SCSI devices that poll.  Apple says not
>to poll.  But consider something like an Ethernet box that attaches via
>the SCSI port, such as Dove's FastNet SCSI, or the similar box from
>Kinetics ( I don't remember what they call theirs ).  These things have
>to poll, since there are no interrupts from SCSI.

I don't understand what Apple means by that.  I conjectured that they just
meant that the OS can't support Disconnect-Reselect protocol, wherein the
target device initiates a reselection.  'Polling' from the CPU side is safe,
since each SCSI transaction goes to completion before you give up the CPU.

Marc Kaufman (kaufman@polya.stanford.edu)