Using standardized SI prefixes

Scott James Remnant scott at ubuntu.com
Wed Jun 13 16:07:57 UTC 2007


On Wed, 2007-06-13 at 08:46 -0600, Kevin Fries wrote:

> As larger and larger sizes are used, what was once an minor difference,
> is starting to become significant.  It almost reminds me of that old
> scam of taking the rounded portions of a penny in financial calculations
> and putting into an account.  It adds up fast.
> 
Not relevant, we're talking in terms of gigapounds here.  If you're
doing calculations in gigapounds, you are inherently rounding.

> This goes way beyond "approximate".  Imagine if you went to the gas
> station to by a gallon (litre for our Europeans) of gas for your car,
> but only received 85% of the gas you thought you paid for.  Now how do
> you feel about how close enough the differences are?
> 
Wrong way around.

If I buy a 100GB drive, and I am ignorant of the fact that "byte" is not
an SI unit, I would be expecting 100,000,000,000 bytes.  If the drive
manufacturer uses the common power-of-2 multiple meaning of gigabyte,
then I would receive a drive that can store 107,374,182,400 bytes.

I received 107% of the gas I thought I paid for.  I am a delighted
customer.

If I am an educated user, than I am aware that G/giga is not an SI
prefix (because byte is not a BIPM accepted SI unit), and commonly
refers to 2^30 bytes.  I would also be aware that disks are sometima
special case, and that I should check with the manufacturer if the 7%
variance is an issue for me and get the actual size of the disk.

> As unethical and immoral as it is to sell gas without accurately
> reflecting the units/price, it is just as bad for us in the computer
> industry to perpetrate this fraud by misreporting the size of memory,
> drives, etc.
> 
They are not generally misrepresented, and where you could claim they
are by the confusion of the computer standard prefixes and the SI
prefixes, the misrepresentation is always giving you more bytes for your
money than you thought.

Scott
-- 
Scott James Remnant
Ubuntu Development Manager
scott at ubuntu.com
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