[RndTbl] Hardware dimensions

Michael Doob mdoob at cc.umanitoba.ca
Tue Jan 22 09:00:44 CST 2013

On 13-01-21 11:08 PM, roundtable-request at muug.mb.ca wrote:

> Message: 1
> Date: Mon, 21 Jan 2013 15:18:35 -0600
> From: "Adam Thompson" <athompso at athompso.net>
> To: "MUUG Roundtable" <roundtable at muug.mb.ca>
> Subject: [RndTbl] Dimensional hard drives?
> Message-ID: <006b01cdf81c$dfda70a0$9f8f51e0$@athompso.net>
> Content-Type: text/plain;	charset="UTF-8"
> Ever double-check an assumption, only to find it false, and feel like the rug just got yanked out from under your feet?
> Go measure the width of a so-called 3.5" hard drive.  Yeah, go ahead.  It's 4" wide.  Now go measure the width of a so-called 2.5" hard drive.  Uh-huh... it's 2.75" wide.  I just (re-?)discovered that and felt just as cheated as when I found out that the nominal sizes of dimensional lumber are complete B.S.!
> I knew this once upon a time, but I guess I forgot... 5.25" & 3.5" refer to the fact that it fits into the bay where you would have been able to fit a floppy drive accommodating the corresponding-size floppy disk.  I can't find any derivation for why we call a 2.75" drive a 2.5" drive, since there's no such thing as a 2.5" floppy[1]!  Perhaps the internal platter is 2.5" wide?
> (See: http://en.wikipedia.org/wiki/Hard_disk_drive#Form_factors)

If it means anything, I just measured a 5 1/4 inch floppy, and it is indeed 5 1/4 inches wide.
I also measured an 8 inch floppy (am I a packrat or what?) and it is 8 inches wide.
I suppose the 5 1/4 inch drive was supposed to hold a 5 1/4 inch floppy. At least that would
make the name logical.


Michael Doob                    Telephone: (204) 474-9796
Department of Mathematics       Fax: (204) 474-7606
University of Manitoba          email: Michael_Doob at umanitoba.ca
Winnipeg, MB, Canada R3T 2N2

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