Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!cs.utexas.edu!uunet!nuchat!moray!siswat!buck
From: buck@siswat.UUCP (A. Lester Buck)
Newsgroups: comp.unix.i386
Subject: Re: 1540 and sync. SCSI drives
Keywords: SCSI AHA1540 386/ix ISC
Message-ID: <459@siswat.UUCP>
Date: 4 Oct 89 02:22:35 GMT
References: <307@dksoft.incom.de>
Organization: Photon Graphics,  Houston
Lines: 24

In article <307@dksoft.incom.de>, dirk@dksoft.incom.de (Dirk Koeppen) writes:
> Does it work to connect a synchronous (4 MB/sec) disk drive and
> an asynchronous (1.5 MB/sec) streamer onto the same SCSI bus on
> the 386/ix Adaptec 1540 controller ? Does the driver switch the
> disk drive into sync. mode or does it use both devices at async
> mode ?
> 
> 
> thanx,
> dirk@incom.de

Sure, SCSI is downwardly compatible.  Everything on the SCSI bus is
asynchronous until the (negotiated) data phase, then a synchronous
transfer can occur.  SCSI-2's wide-SCSI and fast-SCSI are just
variations on this theme.  The negotiation occurs completely transparently
to the driver by an exchange of messages between the device (target)
and the host adapter (initiator).  You can mix and match asynch and
synch devices at will.  The one trick is that fast-SCSI is very touchy
and all your devices must be rated fast, so you won't be able to
mix and match in that case.


-- 
A. Lester Buck		...!texbell!moray!siswat!buck