Path: utzoo!utgpu!watserv1!watmath!att!att!linac!uwm.edu!ux1.cso.uiuc.edu!ux1.cso.uiuc.edu!m.cs.uiuc.edu!gillies
From: gillies@m.cs.uiuc.edu
Newsgroups: comp.arch
Subject: Re: why is 33 MHz a popular number?
Message-ID: <3300230@m.cs.uiuc.edu>
Date: 28 Nov 90 00:51:00 GMT
References: <90@<TOM>
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Nf-ID: #R:<TOM:90:m.cs.uiuc.edu:3300230:000:693
Nf-From: m.cs.uiuc.edu!gillies    Nov 27 18:51:00 1990


Possibly the harmonic numbers multiplied by 100:

CPU Speed	Change				Speed of Instruction
						Fetching
1/6 = 16Mhz						
1/5 = 20Mhz	20% speed increase over 16Mhz	50ns/ins
1/4 = 25Mhz	25% speed increase over 20Mhz	40ns/ins
1/3 = 33Mhz	33% speed increase over 25Mhz	30ns/ins
1/2 = 50Mhz	50% speed increase over 33Mhz	20ns/ins

Don't ask me where 40Mhz came from.

this pattern suggests that the next generation of chips beyond 50Mhz
will run at 100Mhz!  8-)

Maybe this spectrum is something that marketing figured out.  Or maybe
it is the optimal space-time set of speed test-points for a CPU chip
tester.  Or maybe it has something to do with the availability of
high-speed DRAM and SRAM.