Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uwm.edu!ux1.cso.uiuc.edu!shair From: shair@ux1.cso.uiuc.edu (Bob Shair) Newsgroups: comp.arch Subject: Re: why is 33 MHz a popular number? Message-ID: <1990Nov27.192504.11191@ux1.cso.uiuc.edu> Date: 27 Nov 90 19:25:04 GMT References: Organization: University of Illinois at Urbana Lines: 24 tom@ssd.csd.harris.com (Tom Horsley) writes: >Is there some hardware related magic about certain clock rates that makes it >likely for totally different manufacturers of totally different chips to >come out with chips with the same clock rates in similar time frames? >Obviously they all need to stay competitive, but why do they lots of them >wind up at exactly 33? Why not 30 or 35? Actually the magic looks to be in the human mind. For the same reason that events are scheduled to start at 8PM rather than at 8:17, designers set out to build chips with 50ns, 40ns, 30ns cycle times. The new IBM RISC 6000 model 550, at 41.6MHz or 24ns, may be something of an exception. I'll be interested to see whether anyone else uses that rate. Come to think of it, the 540 also runs at a somewhat unusual rate of 30MHz. -- Bob Shair shair@chgvmic1.iinus1.ibm.com Scientific Computing Specialist SHAIR@UIUCVMD (bitnet) IBM Champaign