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From: stevem@hpvcfs1.HP.COM (Steve Miller)
Newsgroups: comp.sys.mac.hardware
Subject: Re: Quantum HD's
Message-ID: <19640008@hpvcfs1.HP.COM>
Date: 19 Jan 90 23:49:39 GMT
References: <1030@ux.acs.umn.edu>
Organization: Hewlett Packard, Vancouver, WA
Lines: 29

>A friend just bought a Quantum ProDrive 40, which was advertised as
>having "12ms access time."  However, SCSI Evaluator reports this time
>as being _22ms_.  I tried the same test on my SE/30's Quantum 40
>[mine is Apple-supplied] and got the same results.  What's going on
>here?  has he gotten a bum drive, or what?


You're comparing "Marketing Math" with a real benchmark.  It's a little like
testing a 200 CPS dot matrix printer or an 8 page per minute laser printer.
Printers rarely deliver the performance rated by the manufacturer unless under
special circumstances.  Or how about those 50 MIPS processors everyone is
talking about ... right!

Naturally, you would expect the drive manufacturers to be actually giving
you numbers based on real throughput tests.  HA!  Of course I can't vouch
for the accuracy of "SCSI Evaluator" either.  I tested my Quantum 105 and
my Quantum 40 and I got similar results, though I can't recall the real
numbers.  All I know is that the Quantums are certainly the fastest drives that
I have ever "driven".  If all manufacturers "lie" to the same degree then you
can at least use their numbers for relative comparisons.

Also remember that the Quantum has a raw access time of about 19ms and the 12ms
number is based on the performance of the drives 64Kbyte cache.  The degree
to which this cache helps is dependent on how the drive is used, it's
possible that the cache doesn't help at all for the "SCSI Evaluator" because
of the way the evaluator does it's testing.


Steve