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Path: utzoo!watmath!clyde!rutgers!lll-lcc!ptsfa!ihnp4!cuae2!ltuxa!ttrdc!ttrde!fjo
From: fjo@ttrde.UUCP
Newsgroups: comp.periphs,comp.sys.mac
Subject: Re: Making a Mac talk SCSI to a Sun
Message-ID: <186@ttrde.ATT.COM>
Date: Mon, 16-Feb-87 10:45:43 EST
Article-I.D.: ttrde.186
Posted: Mon Feb 16 10:45:43 1987
Date-Received: Tue, 17-Feb-87 18:49:28 EST
References: <2594@phri.UUCP> <1784@hoptoad.uucp> <540211194.20192@minster.UUCP>
Organization: AT&T, Skokie, IL
Lines: 13
Summary: Mac+ SCSI speed limit
Xref: watmath comp.periphs:210 comp.sys.mac:1326

In article <540211194.20192@minster.UUCP>, martin@minster.UUCP writes:
> 
> PS
> 	The review of the Mac+ in November '86 Byte states that the
> throughput of the SCSI interface is 320K bytes per second; does anyone
> know if it is really this slow? SCSI is rated at 10M Bits (= 1.25 M Bytes)
> per second, where is the factor of (almost) four going?

The SCSI speed limit on the Mac+ is due to the fact that there is no
DMA used for SCSI data transfer. All data transfer (in good Apple 
"squeeze every drop of power from the CPU" tradition) is done directly
by the 68000.  Perhaps this will change on the MacII?