Path: utzoo!attcan!uunet!husc6!think!ephraim
From: ephraim@think.COM (Ephraim Vishniac)
Newsgroups: comp.sys.mac
Subject: Re: Reeks on Disktimer (LONG)
Message-ID: <31573@think.UUCP>
Date: 15 Nov 88 22:02:02 GMT
References: <698@mouse.UUCP> <30643@think.UUCP> <989@ccnysci.UUCP>
Sender: news@think.UUCP
Reply-To: ephraim@vidar.think.com.UUCP (Ephraim Vishniac)
Organization: Thinking Machines Corporation, Cambridge MA, USA
Lines: 25

In article <989@ccnysci.UUCP> alexis@ccnysci.UUCP (Alexis Rosen) writes:
+In article <30643@think.UUCP> ephraim@vidar.think.com.UUCP (Ephraim Vishniac)
+writes (in an article about J. Reeks vs. DiskTimer II):
+>                        ... As I mentioned in an earlier posting, data
+>transfer rate is highly overrated as a performance measure.  When
+>running most applications, seek time is much more important.

+This is what I used to think. ...  Later I bought a Quantum 80 MB
+unit with a seek time 50% slower than the Maxtor (28 ms as opposed to
+18 ms) which nevertheless performed much faster in many operations.
+The speed came from use of the then-new "fake DMA" mode which used
+hardware-assisted "blind" reads and writes on the Mac II. So transfer
+speed had a major impact on perceived speed.

But the Q280 also has a large (60KB?  I don't remember exactly.)
on-board cache.  So the seeks may be slower, but they are also
somewhat less frequent.  This is a prime example of why benchmarking
or buying disks is so damned complicated.  We need an actual usage
test, but I doubt we'll ever agree on one.

Ephraim Vishniac					  ephraim@think.com
Thinking Machines Corporation / 245 First Street / Cambridge, MA 02142-1214

     On two occasions I have been asked, "Pray, Mr. Babbage, if you put
     into the machine wrong figures, will the right answers come out?"