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From: wunder@orac.HP.COM (Walter Underwood)
Newsgroups: comp.arch
Subject: Re: why is 33 MHz a popular number?
Message-ID: <2770002@orac.HP.COM>
Date: 27 Nov 90 18:57:56 GMT
References: <TOM.90Nov27065615@hcx2.ssd.csd.harris.com>
Organization: HP Software Engineering Systems, Sunnyvale CA
Lines: 27


   I see a lot of the current and near current top of the line RISC chips and
   other microprocessors coming out with a 33MHz clock rate. In a similar way
   the previously most popular number seemed to be 25MHz.

Get out your slide rule and find the L and D scales.  As the exponent
goes through 0.0, 0.1, 0.2, ..., 10**x gives this series:

  1.0
  1.25
  1.6
  2.0
  2.5
  3.2
  4.0
  5.0
  6.3 (or 6.4 if you want it to be 2x 3.2)
  8.0
 10.0

Do these clock speeds sound familiar:  4, 6, 8, 10, 12.5, 16, 20, 25?
Sounds like 33 MHz was an attempt at one-upmanship, and everyone caught
on.

One other common place to see this series is in ANSI film speeds.

wunder