Path: news.eternal-september.org!eternal-september.org!.POSTED!not-for-mail From: Stephen Fuld Newsgroups: comp.arch Subject: Re: base and bounds, Why I've Dropped In Date: Mon, 16 Jun 2025 10:56:40 -0700 Organization: A noiseless patient Spider Lines: 48 Message-ID: <102plso$1od86$1@dont-email.me> References: <0c857b8347f07f3a0ca61c403d0a8711@www.novabbs.com> <102hpk6$3j0bk$2@dont-email.me> <102mv45$lkr$3@gal.iecc.com> <102n693$137tt$1@dont-email.me> <102n7r9$2cog$1@gal.iecc.com> <102o50i$1decq$1@dont-email.me> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Injection-Date: Mon, 16 Jun 2025 19:56:41 +0200 (CEST) Injection-Info: dont-email.me; posting-host="877ae013ce74ddc5db88e977764ff87f"; logging-data="1848582"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX1839wT/FX2MMVi/iXLhYaXGrF/TEjTiX6c=" User-Agent: Mozilla Thunderbird Cancel-Lock: sha1:Wmav1994F+9CyDinEwu4IcC+q7A= Content-Language: en-US In-Reply-To: On 6/16/2025 10:42 AM, MitchAlsup1 wrote: > On Mon, 16 Jun 2025 4:02:26 +0000, Stephen Fuld wrote: > >> On 6/15/2025 1:09 PM, MitchAlsup1 wrote: >>> On Sun, 15 Jun 2025 19:44:41 +0000, John Levine wrote: >>> >>>> According to Stephen Fuld  : >>>>> [ base and bounds vs paging >>>>> An interesting question is whether it is worthwhile to do both. >>>> >>>> Multics had segments of variable size, with each segment paged. >>>> That worked, give or take the inevitable problem of running out of >>>> address bits. >>>> >>>> I think that is an insoluble problem with base and bounds.  However >>>> you divide up the address space into sections, some sections will >>>> be too small. >>> >>> Who was it that said:: The worst error a computer architect >>> can make is to specify insufficient number of address bits ?? >>> >>> Gordon Bell ? >>> >>> Base and bunds simply doubles down on avoiding this rule. >> >> I am not sure what you are saying here. > > Often base ends up with too few address bits, > almost always bounds ends up with too few size bits. But since these can be/should be/are hidden from the user, they can be expanded at will. > On a machine today, wanting byte alignment and bite sizing of > memory areas, you need 64-bits of base, 64-bits of bounds and > about 5 more bits to control things. {{Now while I would not > call someone doing base-bounds sane today--I would claim that > knocking a couple bits off the top of bounds and another couple > of bits of bounds to make the control point fit a control register > container might be considered "sane"}} :-) -- - Stephen Fuld (e-mail address disguised to prevent spam)