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From: beard@ux5.lbl.gov (Patrick C Beard)
Newsgroups: comp.sys.mac.programmer
Subject: Re: async write to disk (MPW C)
Message-ID: <9341@dog.ee.lbl.gov>
Date: 29 Jan 91 16:34:24 GMT
References: <1016@ra.MsState.Edu>
Reply-To: beard@ux5.lbl.gov (Patrick C Beard)
Distribution: na
Organization: Berkeley Systems, Inc.
Lines: 20
X-Local-Date: Tue, 29 Jan 91 08:34:24 PST

In article <1016@ra.MsState.Edu> krn1@ra.msstate.edu (Ken Newton) writes:
#I am working on a real-time application to run on a Mac fx that 
#requires very fast data collection to disk.

The Macintosh OS is an unsuitable OS if you need asynchronous
access to the hard disk.  The SCSI manager can't work asynchronously in
its current design.  Thus you can't take advantage of DMA on the IIfx until
a later system (later even than system 7).  A new disk driver will be required,
I believe, or a new SCSI manager.

However, under A/UX, DMA can and is being used for disk access speedup on
the IIfx.  Ironically Unix is likely to give you better disk performance,
even though you will probably be spending a lot of time swapping programs
to and from disk.  A/UX has no SCSI manager, just different device drivers.

--
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-  Patrick Beard, Macintosh Programmer                        (beard@lbl.gov) -
-  Berkeley Systems, Inc.  ".......<dead air>.......Good day!" - Paul Harvey  -
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