Xref: utzoo comp.arch:4854 comp.lang.c:10170 Path: utzoo!attcan!uunet!kddlab!ccut!ascgw!fgw!flab!ayumi!yuhara From: yuhara@ayumi.stars.flab.fujitsu.JUNET (== M. Yuhara ==) Newsgroups: comp.arch,comp.lang.c Subject: Re: negative addresses Message-ID: <4000@ayumi.stars.flab.fujitsu.JUNET> Date: 16 May 88 09:54:53 GMT References: <2393@uvacs.CS.VIRGINIA.EDU> <21541@amdcad.AMD.COM> Reply-To: yuhara@ayumi.stars.flab.fujitsu.junet (Masanobu Yuhara) Followup-To: comp.arch Organization: AI Lab. Fujitsu Labs Ltd., Kawasaki, Japan Lines: 44 Posted: Mon May 16 18:54:53 1988 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?? Yes, yes. TRON chip deals an address as an signed integer. On TRONCHIP32, -2**31..-1 is called Shared-semi-Space (SS) which is shared among processes. 0..2**31-1 is called Unshared-semi-Space (US) which is independent among processes. (You can think of SS as System's Space, and US as User's Space). TRON chip architecture is designed to be extensible from 32 bit address space through 48 (TRONCHIP48) to 64 bit address space (TRONCHIP64). If you think SS is 2**31..2*32-1, you will have difficulty when you extend address space. But if you think it is signed, address space can be extended naturally. -2**63 +---------+ / | | / | | / | | / | | -2GB+---------+ -2**31 | | | SS | | SS | | | | | <-- Some system parameters stay here. 0 +=========+ 0 +=========+ (such as reset vector.) | | | | | US | | | +2GB+---------+ 2**31-1 | US | \ | | \ | | \ | | \ | | 2**63-1 +---------+ -- Artifitial Intelligence Division Fujitsu Laboratories LTD., Kawasaki, Japan. Masanobu YUHARA kddlab!yuhara%flab.flab.fujitsu.junet@uunet.UU.NET