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From: markb@denali
Newsgroups: comp.periphs,comp.unix.wizards
Subject: Re: query: new disk drive for VAX
Summary: Disk Performance Comparisons
Message-ID: <20391@sgi.SGI.COM>
Date: 10 Oct 88 19:09:07 GMT
References: <4198@bsu-cs.UUCP> <3531@phri.UUCP> <10199@eddie.MIT.EDU> <10209@eddie.MIT.EDU>
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Organization: Silicon Graphics, Inc., Mountain View, CA
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In article <10209@eddie.MIT.EDU>, jbs@fenchurch.MIT.EDU (Jeff Siegal) writes:
> In article <18529@uflorida.cis.ufl.EDU> seeger@beach.cis.ufl.edu (F. L. Charles Seeger III) writes:
> >|Why spend big bux on SuperEagles when you can get 800 Meg, high speed
> >|5.25-inch Winchesters these days for $3,300 each?
> >Performance, of course.  The new SMD drives and controllers offer
> >3.0 MBps interfaces (24 Mbps).  I belive that these 5.25" drives are
> >limited to about 10 Mbps.
> 
> Not true.  Maxtor offers a version of its drive which supports
> synchronous SCSI and claims 4MB/s transfers.  I do not believe it
> costs much (any?) more than the slower (15 Mb/s, I believe) ESDI
> version.
> 
> Jeff Siegal

Some clarification:

3 MB/s is data xfer rate from the media itself, and SMD can xfer at that
rate.  (actually SMDE)

4 MB/s claim by Maxtor and others is actually burst rate on SCSI, whether
sync or async.  xfer rate from the media itself is 10-15 MHz.

ESDI will blow the doors off SCSI if done correctly.  ESDI can go to
24 MHz, which compares nicely with SMDE.  Currently available drives
are at 15 Mhz.  ESDI bus times are measured in microseconds, while 
SCSI can be looked at in milliseconds.

For performance today, use SMD of some flavor.  ESDI comes in 2nd, and
SCSI is a far 3rd.  ESDI will approach SMD within a year, and the 5.25"
drives are coming with SMD interfaces now, too.

					markb