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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
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Posted: Sat Mar  2 16:50:38 1985
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Josh Knight  quotes:
+---------------
| "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

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