Re: [stella] What's magic about a byte?

Subject: Re: [stella] What's magic about a byte?
From: Chris Wilkson <ecwilkso@xxxxxxx>
Date: Thu, 14 Apr 2005 01:17:58 -0400
Heh.  Yeah, I'm a hardware geek.  :)

Here's another one...a little (not much) less technical, and maybe an urban legend,
but perhaps a bit more interesting from the human-technology interface perspective...

Are Religion/Mythology responsible for "modern" word sizes?

The story:
So MIT was supposed to provide the onboard computers for NASA's Gemini program.
But some authority figure in NASA balked because the plan was for a 13-bit data
word.  "Too unlucky!"  Back to the drawing board.  The irony is that the final Gemini
computers, from IBM, used a 13-bit instruction and a 26-bit data word.  Heh.  A
trilogy of 13's!!!

Rumor has it that the original MIT design was scaled back to 12-bits to make
the superstitious people happy, but it took too long.  The design eventually
became the PDP-8 minicomputer.

Having learned from its mistakes, MIT designed the machine used in Apollo to have
a 16-bit word instead.



On Thu, 14 Apr 2005, Ruffin Bailey wrote:

> On Apr 13, 2005, at 11:57 PM, Chris Wilkson wrote:
> > On Wed, 13 Apr 2005, Ruffin Bailey wrote:
> >
> >> Why would the number of bits in a byte have to have anything to do
> >> with
> >> powers of 2?  The max number, whether 7 bit, 13 bit, or 8 bit would
> >> still be a binary number.  ??
> >
> > Because decoders and encoders using bits as control lines will always
> > address 2^n locations.  Either you implement them, or you don't.  But
> > if you need 5 states, you need 3 bits to represent that.  Then you have
> > created 3 bogus states.  You need to define them or else "Bad Things"
> > can happen.  You can define them by hardwiring, but you might as well
> > make them useful if you can.
> >
> > In the case of decimals digits, you need 4 bits to encode each
> > character
> > with.  If your system is already 6 bits, just to encode the text
> > characters,
> > you're wasting 2 bits when doing BCD.  You might as well make your word
> > 8 bits wide so you can encode 2 digits without waste.
> ... thus earning the behind his email nick. ;^)
> Ruffin Bailey
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