[RndTbl] Dimensional hard drives?

Hartmut W Sager hwsager at marityme.net
Mon Jan 21 17:36:51 CST 2013

 That's hilarious!  It also reminds me of an old tagline:

2 + 2 = 5 for extremely large values of 2.

So, what is the outer width of a 5.25 inch device?  (I know, I could just
go measure a CD/DVD drive, but I'm not near a raw drive right now.)

Yes, your comments are correct as to how these misquoted dimensions came
about.  As for lumber, which is badly misquoted in the other direction
(especially the ubiquitous 2x4), I once heard an explanation for that, but
have forgotten it.  Anyone know?  (Definitely on topic.  I may want to
build a computer rack out of lumber.  [grin])

Hartmut Sager

On 21 January 2013 15:18, Adam Thompson <athompso at athompso.net> wrote:

> 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)
> -Adam
> [1] OK, yes, there a 2.5" floppy did exist briefly, but it was never any
> sort of standard and I've never seen one in person AFAIK.  FYI, the Sony
> micro-floppy format was not 2.5", it was 90mm (closer to 2", anyway).
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