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From: stevew@wyse.wyse.com (Steve Wilson xttemp dept303)
Newsgroups: comp.arch
Subject: Re: Synchronous versus Asynchronous SCSI
Message-ID: <2547@wyse.wyse.com>
Date: 8 Dec 89 23:19:44 GMT
References: <7909@charlie.OZ>
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Reply-To: stevew@wyse.UUCP (Steve Wilson xttemp dept303)
Organization: Wyse Technology
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In article <7909@charlie.OZ> robert@eowyn.cm.deakin.oz.au () writes:
>I would like to find out what happens when you intermix synchronous
>and asynchronous SCSI devices on the one bus? Does the bus drop to
>the lowest common denominator, or does it work at sync speeds to sync
>devices etc.? What happens when both types of devices are doing
>intermixed transfers? Does the speed drop significantly for the sync
>devices? I am thinking here of high speed SCSI disks and slow speed
>cartridge tapes or 8mm tapes. Thanks for any information.
>
>Robert Ruge

Robert,

SCSI will transfer in SYNCH mode to a device that is capable of synch
operations, and to ASYNCH devices that can only transfer in asych mode.
This is a situation where ASYNCH is the lowest common denominator, but
if both the initiator and the target are capable of SYNCH, then they
can use that mode of transfer. 

The above implies that if your system is completely SYNCH capable it
will take full advantage of the improved speed.  If you have a mix,
you'll still get an advantage when talking to SYNCH devices.

Steve Wilson