From: vail@tegra.com (Johnathan Vail)
Subject: Re: SCSI bad sectors?
Organization: Tegra-Varityper, Inc. Billerica, MA
Date: Thu, 1 Oct 1992 18:05:43 GMT



In article <BvFr5D.Bw1@iat.holonet.net> bwilliam@iat.holonet.net (Bill Williams) writes:

   Johnathan Vail, you have made some serious mistakes in your rebuttal to my
   charge that people, such as yourself, are doing a great diservice by
   trying to
   redefine the word Megabyte. In fact you are one of the extremely rare
   people who
   think that a Kilobyte is only 1000 bytes of memory storage.


I can see valid logical claims to both definitions.  You have yet to
convince me that your claim is correct.

The prefixes "mega" and "kilo" are defined in scientific circles to
mean 10^6 and 10^3 respectively.  Is there a new "Mega" and "Kilo"
definition that I am unaware of?  If there is then we just have an
industry problem of the difference between "k" and "K".

Computer memory, because it is addressed using binary signals, almost
always comes in sizes that are powers of two.  When you start counting
memory bytes I would not disagree about using 1024 and 1024^2 since
that is the most logical und useful system for measuring ROM and RAM
memory.  And I haven't seen any instances in the industry where this
differs. 

However, when you start counting bytes of mass storage there is no
longer anything but compatibility with computer systems and operating
systems that make powers of two magic.  Only by convention do most
people use block sizes of 512 or other powere of two bytes.  Counting
bytes by using 1024 bytes to mean k is still useful for most people.

But what if you have blocks of 1000 bytes?  A binary based units
system isn't obvious any more.  Since this is entirely possible with
many (or most) SCSI disks to specify the format used how do you
measure the capacity in the most general case?

In reality several vendors specify the total number of bytes.  Many do
not use "K" or "M" in the literature and only Quantum in the
literature I looked at actually specified their units.  By
implication, Ricoh seemed to use the same system.  Why is this wrong?



    A Megabyte is 1,048,576 bytes of storage. It has always been, and except from
   people in the storage device businness who are motivated by greed, will always
   be so to computer programmers.

This may be a perception or language problem but I think you are going
too far attributing it to greed.  People in the storage business
aren't confined to a binary counting world and use the definitions as
they defined internationally in other disciplines.


   Two products that I helped write for the Macintosh have sold hundreds of
   thousands of copies and the definition of megabyte in them is the correct one.
   In fact, if it was the greedy 4.58% inflated number, IT WOULD NOT MATCH THE
   CALCULATIONS PRESENTED BY APPLE's FINDER. Please change your definition if
   you would.


Contrary to what Apple and their minions would have you beleive, Apple
is not the whole world of computers.  The software I wrote was made to
match the information provided by the drive vendor.  By coincidence it
happened that the Quantum LPS drive was one of more prevelent drives I
was using during development so it was no surprise that my software
matched their system of units.

I haven't seen any evidence to invalidate this system while using it.
Either it matches exactly what the vendor claims (Quantum) or the
drive is rated so generally (IBM) that the units don't matter.

And since computers usually don't read advertising literature they
won't be confused in any case.  When you do a READ CAPACITY you get
the number of blocks as absolute discrete units.


   >"If this is not right I would be happy to be corrected."

   Glad to help out.


Except you only added more conspiracy theories and an appeal that
"Apple did it this way."  Apple doesn't make disk drives.

It is a small thing to change the calculation in my software and
believe that drives should be measured in "Megabytes" of 2^20.  Until
someone offers some real arguments I am not convinced to do so.


jv


"The time of day is no secret, but Apple still doesn't
 deserve the time of day." - RMS
 _____
|     | Johnathan Vail     vail@tegra.com     (508) 663-7435
|Tegra| jv@n1dxg.ampr.org    N1DXG@448.625-(WorldNet)
 -----  MEMBER: League for Programming Freedom (league@prep.ai.mit.edu)

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