Path: utzoo!mnetor!tmsoft!torsqnt!news-server.csri.toronto.edu!cs.utexas.edu!usc!zaphod.mps.ohio-state.edu!ub!uhura.cc.rochester.edu!rochester!pt.cs.cmu.edu!o.gp.cs.cmu.edu!andrew.cmu.edu!mh2f+
From: mh2f+@andrew.cmu.edu (Mark Hahn)
Newsgroups: comp.arch
Subject: re: 64 bit addresses
Message-ID: <cbiAekK00VpINR8nEq@andrew.cmu.edu>
Date: 13 Feb 91 05:12:16 GMT
Organization: Carnegie Mellon, Pittsburgh, PA
Lines: 17

Just think of the added overhead in pointer-linked structures!
Big addresses are a major win for typed support though, since
more big-bag-of-pages 'tag' bits are available.  (NB: not 
a portability violation.)  It also makes for a dandy hash function 
for names up to 8 chars!  I guess the whole point is to make large, 
sparse structures feasible, since it doesn't seem realistic 
to do _anything_ in 64bit (~2e19) quantities:

RAM: 1M simms @ $50	5e1/1e6		$1e15
hard disk 1.2G @ $3k	3e3/1e9		$6e13
gigabit net or
fast memory bus 	1/1e8		2e11 sec (millennia)

On the other hand, 32bits (~4e9) is just $2e5 RAM, $1e4 disk, 40 sec.
On the first hand again, perhaps CS needs a superproject, too!

regards, mark