Re: GB vs. MB

Leonard N. Zubkoff (
Wed, 27 Nov 1996 17:06:44 -0800

Let's face it -- the original fault with KB/MB is in using the same prefixes
that already had definitions for a different purpose. The scientific community
has used K for kilo = 1000 and M for mega = 1000000 for quite a long time. The
computer industry blew it badly by using K/kilo and M/mega for incompatible
purposes. The marketeers have certainly done their part to encourage whichever
interpretation looks bigger, but they didn't create the original problem.

It would be one thing if there were no overlap between computer and scientific
uses, but that just isn't so. For example, the PCI bus can burst transfer at a
theoretical maximum frequency of 33.0MHz times 4 bytes/transfer. So you would
think that this totals 132.0 MB/second, and indeed that's the way it is usually
reported. But that MB is million, not 2^20. If we insist on MB meaning 2^20,
we only get 125.885MB/second. A similar problem occurs in other cases where
mega is used in a frequency or 1/time context, such as Fast SCSI-2 being 10.0
mega-transfers/second. With MB = 2^20 Fast SCSI-2 is only good for 9.54
MB/second. We can't just move "mega" around without thinking in these

Since there's no truly consistent way to view this, I don't really care that
much which way it's reported, so long as a footnote clearly specifies which
meaning pertains. Since I've been working with SCSI a lot lately, I'm just as
happy with MB = million for storage devices since it keeps the time/space
computation easy.