Newsgroups: comp.arch
Path: utzoo!henry
From: henry@utzoo.uucp (Henry Spencer)
Subject: Re: 64-bit addresses
Message-ID: <1990Feb12.232740.21387@utzoo.uucp>
Organization: U of Toronto Zoology
References: <9708@spool.cs.wisc.edu> <20270@cfctech.cfc.com> <11112@encore.Encore.COM> <753@dgis.dtic.dla.mil>
Date: Mon, 12 Feb 90 23:27:40 GMT

In article <753@dgis.dtic.dla.mil> jkrueger@dgis.dtic.dla.mil (Jon) writes:
>Are 64 bit spaces being held back by hardware: complexity, fabrication,
>critical paths?  Or software (what we used to call systems software):
>virtual memory operating systems that can give processes 64 bit virtual
>spaces at acceptable cost?...

Neither, really.  They're being held back by limited customer demand.
Cranking up all the pointers to 64 bits -- and probably all the integers
too, given the sloppy assumptions in a lot of code -- will cost quite a
bit in space even if the time cost is nil.  Also, given certain other
sloppy assumptions, porting to such a machine will be a lot of work.
There are relatively few applications that would find this cost-effective
right now; *most* programs find 32 bits ample.
-- 
SVR4:  every feature you ever |     Henry Spencer at U of Toronto Zoology
wanted, and plenty you didn't.| uunet!attcan!utzoo!henry henry@zoo.toronto.edu