# 2.5" disk - what do 1/4H, 1/6H, 1/8H mean?

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I'm looking at a replacement laptop disk. Some sites now list some disks as
2.5" x 1/8H, 2.5" x 1/6H, 2.5" x 1/4H (or just simply as 2.5"). I'm not
familiar with the 1/4H (etc) designation, could someone tell me what it
means and how I can tell from my existing disk which I need?

TIA.
--
Brian Cryer
www.cryer.co.uk/brian

## Re: 2.5" disk - what do 1/4H, 1/6H, 1/8H mean?

It refers to the height, but I'm not sure of the correspondence between the
number given and the physical height (thickness). 1/8H corresponds to .4"
(about 10mm) in the randomly chosen spec below:
http://www.provantage.com/toshiba-hdd2d15-50pk~7TOSD036.htm

on another 1/4H corresponded with 19 mm.

## Re: 2.5" disk - what do 1/4H, 1/6H, 1/8H mean?

I think it refers to the size of drive bay the disk is intended for, rather
than the actual measurement of the drive.

## Re: 2.5" disk - what do 1/4H, 1/6H, 1/8H mean?

I think you are right, although it strikes me that if the folk on this
newsgroup are uncertain about it then the manufacturers are not giving very
clear data here!

## Re: 2.5" disk - what do 1/4H, 1/6H, 1/8H mean?

On Fri, 12 Jan 2007 17:31:05 +0100, "Dave"

Manufacturers generally spec in actual millimeter height,
not 1/2H, etc.  The surest bet is to measure the drive caddy
in the laptop, what max size drive would fit in it, and
compare to the specific drive model, manufacturer's
datasheet.

## Re: 2.5" disk - what do 1/4H, 1/6H, 1/8H mean?

Dave wrote:

The original floppy drives, both 8 inch, and 5 inch, were 3 1/2"
high.  The fractions are referred to that.  When they got down to
1/2 size in 5 inchers the price dropped to about \$50 each.  Now
they go for 5 to 10.  Hard drives just followed the same form
factor.

--
"I was born lazy.  I am no lazier now than I was forty years
ago, but that is because I reached the limit forty years ago.
You can't go beyond possibility."              -- Mark Twain

## Re: 2.5" disk - what do 1/4H, 1/6H, 1/8H mean?

Dave wrote:

I believe that it's the 'height' of the drive, expressed as a fraction of
the old 'full height' drives.

A full height drive is around 80mm. (An optical drive is classed as
half-height, around 40mm.) Therefore the numbers represent one eigth of
~80mm, or one quarter of ~80mm etc.

At least that's my take on it.
--
Shaun.

## Re: 2.5" disk - what do 1/4H, 1/6H, 1/8H mean?

I can't say I've ever seen the 1/8, 1/6, 1/4 designations before.

Most sites measure drives in height by mm - millimeter.  I'd suggest
looking up the drive that's in your laptop and confirming it's size at
the manufacturer's web site and then find one with comparable physical
specifications.

-Lee

Brian Cryer wrote:

## Re: 2.5" disk - what do 1/4H, 1/6H, 1/8H mean?

leew wrote:   *** and top-posted - fixed ***

with) the material you quote, after snipping irrelevancies.

IIRC "Full Height" refers to 3 3/4 inch high units, thus 1/2 is 1
7/8 inches, etc.

--
Chuck F (cbfalconer at maineline dot net)
Available for consulting/temporary embedded and systems.
<http://cbfalconer.home.att.net

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