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Article #32588Re: 16MHz board -- fast CPU, slow memory?
From: Gert Slavenburg
Date: Thu, 19 May 1988 00:34
Date: Thu, 19 May 1988 00:34
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According to some local statistics of 68000's in operation, a crude approximation is that a 68000 spends approximately half of its cycles internal and half externally (due to memory reference statistics). The external cycles still take the same amount of time, the internal cycles go twice as fast. Hence, what used to take 'n' seconds, now takes '0.75*n' seconds. Or at most a performance of 1.33 * that of an ST with a 8 MHz processor. Add to this the fact that there is an increased number of memory requests per time unit, and hence more collisions with the video accesses (if this applies on the ST, I'm not sure). This would lower the performance a little more. So you get somehwere between a 1.2 to 1.33 * speedup, roughly. I wouldn't consider that enough of a speedup in relation to the expected cost.
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Path: arc1-ca.pugleaf.net!utzoo!attcan!uunet!lll-winken!lll-tis!ames!pasteur!ucbvax!hplabs!pyramid!prls!gert From: gert@prls.UUCP (Gert Slavenburg) Newsgroups: comp.sys.atari.st Subject: Re: 16MHz board -- fast CPU, slow memory? Summary: approximately 33 % gain Message-ID: <11652@prls.UUCP> Date: 19 May 88 00:34:54 GMT References: <725@cacilj.UUCP> <5607@chinet.UUCP> Reply-To: gert@prls.UUCP (Gert Slavenburg) Organization: Philips Research Labs, Sunnyvale, California Lines: 15