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

Message: 1 Date: Mon, 21 Jan 2013 15:18:35 -0600 From: "Adam Thompson" athompso@athompso.net To: "MUUG Roundtable" roundtable@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.

Cheers, Michael