Reiability of wrong media (was: is out of 5-1/4" diskettes

From: Pete Turnbull <pete_at_dunnington.u-net.com>
Date: Fri Jan 22 02:56:09 1999

On Jan 21, 21:07, Sam Ismail wrote:
> Subject: Re: Reiability of wrong media (was: is out of 5-1/4" diskettes
> On Thu, 21 Jan 1999, Megan wrote:
>
> > I think the problem with '1.44 Mb' is that IBM chose to refer to
> > the exact number of bytes without using the power-of-two term
> > properly.
> >
> > For example... on pdp-11s, the virtual address space is always
> > referred to as 64 Kb... but the actual max (byte) address is
> > 65535. If we were to follow what it appears IBM did, we would
> > have been referring to 65.5 Kb.
>
> No, a megabyte is not a power of two number. A megabyte = 1,000,000
> bytes. So 1.44 megabytes = 1.44 million bytes = roughly 1,440,000 bytes.
>
> So 1.44MB disk drive is not a misnomer.

As Megan pointed out, the maths is wrong. A "1.44MB" disk has 80
cylinders, two sides, 18 sectors per track, sector size 512 bytes.

80 * 2 * 18 * 512 = 80 * 18 * 1024 = 1440KB

That's where the "1.44" number comes from.

And a Megabyte is normally held to be 1024 * 1024 (megabyte would, I agree,
be different, 1000 * 1000). But "1.44MB" refers to 1.44 * 1000 * 1024,
which is a ridiculous way to count. 1440KB = 1.406MB.

-- 
Pete						Peter Turnbull
						Dept. of Computer Science
						University of York
Received on Fri Jan 22 1999 - 02:56:09 GMT

This archive was generated by hypermail 2.3.0 : Fri Oct 10 2014 - 23:32:08 BST