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From: solomon@chaos.utexas.edu (Thomas Solomon)
Newsgroups: comp.periphs.scsi
Subject: Asynchronous vs. synchronous transfer and bus-mastering
Message-ID: <49214@ut-emx.uucp>
Date: 19 May 91 16:22:21 GMT
Sender: news@ut-emx.uucp
Reply-To: solomon@chaos.utexas.edu (Thomas Solomon)
Organization: University of Texas at Austin, Center for Nonlinear Dynamics
Lines: 24

This is probably a question that is obvious to most of the people
in this group, but I'm new to the world of SCSI, so bear with me.

I've heard of both synchronous and asynchronous mode for SCSI
transfers.  In all of the spec sheets that I have seen for disk
drives and controllers, the synchronous mode is alway substantially
faster.  We have an application that will require us to squeeze
every ounce of performance from our disk drive.  We will be running
just one task when we need this performance, so I would think that
we would be able to synchronize whatever needs to be synchronized
to run in the faster mode.

My question:  can anyone describe the difference between sync. and
asynch. mode, or point me in the direction of a FAQ file or magazine
article that will explain this difference?  I need to know not only
the differences between synch and asynch, but also how one goes about
using the synch. mode.  Also, can disk performance be improved by
using the bus-mastering DMA capabilities of the new EISA SCSI cards,
and if so, how?

Thanks.

				Tom Solomon
				solomon@chaos.utexas.edu