Segmentation in real mode
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From: wolfgang kern on 12 Mar 2005 14:20 Tom asked: | Ladies and gentlemen, :) | Thank you ALL very much for your most instructive replies. I will study | them all thoroughly. | | My question, however, remains: | | Why absolute address = segment *16 + offset, and not just | absolute address = segment + offset. | | So, why the division (first) and multiplication (back again)? | | I understand I can take it the way it comes, still, there needs to be a | sensible because to this why. Yes: Once Intel decided to make a CPU for larger memory than 64Kb, the designers were allowed to use a few more 16-bit registers to cover (the very huge range at this time) 1 Mb of memory. Why: The decision for an even distribution of the 'new-16 bit' segments sounds logical (at least in the view from the past). Unfortunately all following CPUs, including late AMD/EMT64, are made backwards compatible to this ancient 8086 chip. Protected mode was the attempt to make segments larger, but here some paranoid influence for protection made the story needless complicated. __ wolfgang
From: Betov on 12 Mar 2005 16:24 "wolfgang kern" <nowhere(a)nevernet.at> ýcrivait news:d0vflt$8iv$1 @newsreader1.utanet.at: > Why: > The decision for an even distribution of the 'new-16 bit' segments > sounds logical (at least in the view from the past). :) It did not seemed that logical to everybody, at that time, i recall having read a paper (maybe from Eric Isaacson), where the guy said that he was there, as a young fellow, at Intel, at that time, and did not understood why the talking head took that decision... and that he only understood several years later why and how it was as absurd as it first seemed to him. :) Thinking of the CPU producers as Assembly experts, by definition, is an error that you should not do, given the massive evidences you have, nowadays, where they clearly show that they do not even know that Assembly is still used by some, and what it could even be... ;) Betov. < http://rosasm.org/ >
From: Annie on 12 Mar 2005 20:47 On 2005-03-12 BethStone21(a)hotmail.NOSPICEDHAM.com wrote: > [ ... 207 lines -- snipped ... ] _____ Crikey. Get a life, Beth. ((( `\ Hehe! _ _`\ ) (^ ) ) ~-( ) _'((,,,))) ,-' \_/ `\ ( , | `-.-'`-.-'/|_| \ / | | =()=: / ,' aa
From: Beth on 12 Mar 2005 23:28 Annie wrote: > Beth wrote: > > [ ... 207 lines -- snipped ... ] > > Crikey. Get a life, Beth. Hehe! I was merely countering your typically malicious posting, Annie... Simply, if you didn't want a response then you shouldn't have made spuriously inaccurate accusations...because, you see, I fully assure you that, in such cases, I _WILL_ counter them every single time... As I was saying, you're like a moth with a lightbulb or a fly with a window...you fly towards it - BANG! - you smack your head...then you try it again...then you try it again...failing to comprehend the "relationship" that, simply, if you stopped banging your head against the window, then it wouldn't hurt your head so much... If you don't want my responses, then _STOP INVITING THEM_ by posting your malicious spew requiring the need to counter their "malicious rumours", as you always do...if you never posted such things, then I'd have absolutely no need to post "207 lines snipped" responses to them... Do you see how this works? It's a very simple thing, really... When I post - though I might not always like what I see in response - I do so fully _welcoming_ discourse and responses ("I may disagree with what you have to say, but I shall defend, to the death, your right to say it", quote commonly misattributed to Voltaire but is actually a translation of a line from "Les Liaisons dangereuses" or "Dangerous Liasons" in English...mind you, though we may disagree where the quote originates from, I do, indeed, defend people's right to misattribute it to Voltaire as much as they like ;)... If you want to give "monologues", Annie, then could try "public access TV" or something...Queen of the airwaves with your "all-new all-American all-paranoid-delusional Annie ASCII show"!! Hey, I'd watch it...once...for about a minute...maybe...just for a laugh... Beth :)
From: Annie on 13 Mar 2005 01:42
On 2005-03-13 BethStone21(a)hotmail.NOSPICEDHAM.com said: > I was merely countering your <*SNIP*> _____ Aw, c'mon now, cariad...when are ((( `\ you gonna invite me over to your _ _`\ ) flat for tea? (^ ) ) ~-( ) We could have some nice cawl, _'((,,,))) some laverbread and bara brith. ,-' \_/ `\ And, of course, I'd want you ( , | to fix me some of your famous `-.-'`-.-'/|_| crempog. With whipped cream on \ / | | the side. =()=: / ,' aa Can you pick me up in Swansea? Oh; that's right...you don't have a car. No problem. I'll rent one. Hehe! |