Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.1 6/24/83; site redwood.UUCP Path: utzoo!watmath!clyde!burl!ulysses!allegra!mit-eddie!genrad!decvax!tektronix!hplabs!hpda!fortune!redwood!rpw3 From: rpw3@redwood.UUCP (Rob Warnock) Newsgroups: net.arch,net.micro.16k,net.micro.68k Subject: Re: 24 bit vs. 32 bit address space Message-ID: <181@redwood.UUCP> Date: Sat, 2-Mar-85 16:50:38 EST Article-I.D.: redwood.181 Posted: Sat Mar 2 16:50:38 1985 Date-Received: Wed, 6-Mar-85 03:12:44 EST References: <983@watdcsu.UUCP> <2385@nsc.UUCP> <730@amdcad.UUCP>, <2393@nsc.UUCP> <295@cmu-cs-spice.ARPA> <133@v1.UUCP> Organization: [Consultant], Foster City, CA Lines: 29 Xref: watmath net.arch:921 net.micro.16k:246 net.micro.68k:632 Josh Knightquotes: +--------------- | "The biggest (and most common) mistake that can be made in a computer design | is that of not providing enough address bits for memory addressing and | managment" | Bell and Mudge, "The Evolution of the PDP-11" in _Computer_Engineering,_A_ | _DEC_View_of_Hardware_Systems_Design, Digital Press, 1978. +--------------- (That's on page 381, for any interested.) Turn the page (to 382), and they say: "In retrospect, it is clear that another address bit is required every two or three years, since memory prices decline about 30 percent yearly, and users tend to buy constant price sucessor systems." So if you are designing a processor family to last at least a decade, add AT LEAST 5 bits to what you think is "reasonable" now (more, for safety). I personally think we will see people complaining about 32 bits (based on real needs) BEFORE the current decade is out. Rob Warnock Systems Architecture Consultant UUCP: {ihnp4,ucbvax!dual}!fortune!redwood!rpw3 DDD: (415)572-2607 USPS: 510 Trinidad Lane, Foster City, CA 94404