

The IBM PC ran at 4.77MHz due to a decision made in 1953 - petercooper
http://dosmandrivel.blogspot.com/2009/03/ibm-pc-design-antics.html

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indrax
Reminded me of this:
[http://en.wikipedia.org/wiki/Track_gauge#Early_origins_of_th...](http://en.wikipedia.org/wiki/Track_gauge#Early_origins_of_the_standard_gauge)

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drudru11
Tim,

Almost all computers back then clocked off of a color burst. Apple 2 for
example.

Why?

Those crystals were super cheap compared to others.

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yuhong
Even most of today's computers ultimately generate their clock off the color
burst, though with more complex circuitry.

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duskwuff
Wait, what? The "color burst" is only relevant to analog television signals.
It hasn't been used in computers since we switched away from TV monitors in
the late 1980s. It's definitely not present in today's computers outside a few
video-out circuits (not even VGA, only composite / S-Video output).

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yuhong
False: <http://arstechnica.com/cpu/2q99/bxhack/hacking-bx-2.html>

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Duff
Somehow I don't buy the $0.50 thing. I remember that my dad laid out some
serious coin to "upgrade" from an old TV to a proper monitor.

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DrJokepu
Consumer prices and manufacturing costs are not necessarily related. Consumer
prices include the costs of R&D, marketing, logistics, management, the profit
margins and so on. Moreover, saving $0.50 here and there can greatly reduce
the costs of manufacturing. Often these little savings can make the difference
between making a loss and making a nice profit.

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daemin
Could it also be the fact that good engineers love to optimise design?

Saving another clock or a more complicated divider to achieve the required
video clock rate would be a damn good thing to accomplish. Sure money was also
saved, and together with a few other such savings, multiplying them all by
millions of units, would save quite a lot of money.

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pbhjpbhj
From the article:

> _The color subcarrier is a signal with a frequency of 3.579545 MHz._

So he explained how one choice depend on another seemingly arbitrary choice
but didn't follow up the branch ... anyone want to do one better and explain
why this frequency was chosen? Is it a multiplier of how fast Tesla's dog
chased it's tail?

