Path: utzoo!mnetor!uunet!seismo!sundc!pitstop!sun!amdahl!apple!bcase
From: bcase@Apple.COM (Brian Case)
Newsgroups: comp.arch
Subject: Re: negative addresses
Message-ID: <9485@apple.Apple.Com>
Date: 10 May 88 17:57:26 GMT
References: <2393@uvacs.CS.VIRGINIA.EDU>
Reply-To: bcase@apple.UUCP (Brian Case)
Organization: Apple Computer Inc, Cupertino, CA
Lines: 14

In article <2393@uvacs.CS.VIRGINIA.EDU> wulf@uvacs.CS.VIRGINIA.EDU (Bill Wulf) writes:
>Has anyone ever seen a machine with "negative addresses", that is, one
>where the address space is -2**31..2**31-1 rather than 0..2*32-1??
>Any thoughts on what the problems with such a scheme might be (or are)?

Check out the Elxsi machine.  It has "negative" addressing.  It seems that
with negative addressing, you can get a simple address checking for free.
Put the OS Kernel in negative space, e.g.

>...as far as I can tell, the primary (only?) use
>of unsigned arithmetic is for address computations.

Yeah, same here, unless it's for some obscure purpose or is supported
directly by the source language.