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From: eder@ssc-vax.UUCP (Dani Eder)
Newsgroups: net.micro
Subject: Re: addresses larger than 32 bits
Message-ID: <291@ssc-vax.UUCP>
Date: Fri, 21-Dec-84 11:45:30 EST
Article-I.D.: ssc-vax.291
Posted: Fri Dec 21 11:45:30 1984
Date-Received: Sat, 22-Dec-84 03:15:14 EST
References:  <280@oakhill.UUCP> <1258@orca.UUCP>
Organization: Boeing Aerospace Co., Seattle, WA
Lines: 20

> In discussing addresses larger than 32 bits, remember that those extra
> bits pile up additional memory awfully fast.
> 
> To build a computer with 48-bit addresses and to give it 2**48 memory
> cells, you would need more cells than there are atoms in the Earth.
> Addresses bigger than 48 bits are probably not worthwhile, unless you
> need a discontiguous (sparse) address space.
> 
>   -- Andrew Klossner   (decvax!tektronix!orca!andrew)       [UUCP]
>                        (orca!andrew.tektronix@csnet-relay)  [ARPA]

2**48 =  281.475 trillion.
If you have 8-bit words, and 1 megabit RAM's, you would need
2,147,483,648 of them.  Assuming you need one cubic inch per
RAM, they would fit in a box 100x100x125 feet.  While this
is a very large amount of memory, it is a long way from even
the number of grains of sand on a large beach, let alone the
atoms in the Earth (about 10**50).

Dani Eder / Boeing Aerospace Company / ssc-vax!eder / (206)773-4545