Weekly Classic Computer Trivia Question (20141205)

Fred Cisin cisin at xenosoft.com
Sat Dec 6 14:48:01 CST 2014

On Sat, 6 Dec 2014, Chuck Guzis wrote:
> These are primarily PC distinctions.  The HD 3.5" disk is sold with a
> nominal raw capacity of 2.0MB.  In other words, if you assume a 300 RPM

Yes, we are talking about "formatted capacity" with a very arbitrary
Q: which manufacturer called their 2.8M drive "4M", and quoted the
unformatted capacity?

> But a "360K" 5.25" disk is formatted in PC terms as tracks of 9 sectors
> of 512 bytes or 720 sectors total or exactly 360 * 1024 bytes.  So far
> so good.

. . . and, of course, other choices of format parameters, even sticking
with MFM, can lead to 300K to 440K.
"360K" became a relatively unambiguous way to describe it, so long as one
acknowledges that that is in terms of the most prevalent format in use.

> I take hard drive capacities as stated as more-or-less; not exact.  It's
> been the case since the manufacturers started putting printed defect
> maps on the drives.

It was always interesting to note that FDISK used Mebibytes, wheras other
utilities in the same OS used 1,000,000, or even the bizarre 1,024,000

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