Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uunet!mcsun!hp4nl!sci.kun.nl!wn3.sci.kun.nl!ge From: ge@wn3.sci.kun.nl (Ge' Weijers) Newsgroups: comp.arch Subject: Re: why is 33 MHz a popular number? Message-ID: <2525@wn1.sci.kun.nl> Date: 3 Dec 90 12:55:11 GMT References: <2770002@orac.HP.COM> Sender: root@sci.kun.nl Lines: 32 wunder@orac.HP.COM (Walter Underwood) writes: > 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: >One other common place to see this series is in ANSI film speeds. That's a bit different: Common film speeds differ by factors of 2^(1/3). This used to be known as 1 DIN. The ISO scales are: (ISO = ASA + "/" + DIN) ASA 100 = ISO 100/21 (append a degree symbol) ASA 125 = ISO 125/22 (100 * 2^(1/3) = 125.9921....) ASA 160 = ISO 160/23 (100 * 2^(2/3) = 158.74.....) ASA 64 = ISO 64/19 Film speeds come in third octaves. (My Nikon actually gives 32 seconds exposure when set to 30 seconds. All exposure times are rounded from their actual values) Ge' Weijers -- Ge' Weijers Internet/UUCP: ge@cs.kun.nl Faculty of Mathematics and Computer Science, (uunet.uu.net!cs.kun.nl!ge) University of Nijmegen, Toernooiveld 1 6525 ED Nijmegen, the Netherlands tel. +3180652483 (UTC-2) Brought to you by Super Global Mega Corp .com