【4:730】68K v.s. x86 - 1 名前：ナイコンさん 2008/09/07(日) 04:12:36
- 独立させてみた。
Z8Kや658xx、16Bit〜でもOK
- 721 名前：ナイコンさん ：2013/06/08(土) 20:59:51.79
- [Jarrett:] How about the work stations? At this point was that considered to
be a market to focus on?
ワークステーションはどうでしょう? これについて、市場の焦点として考慮しましたか?
[Leukhardt:] Well we thought that was a key market segment for the 386.
It was not a market segment where the 286 was doing well at all;
it was a market segment where the 68000 was cleaning up principally because
the 286 was not viewed as a machine that ran Unix well and the 68000 was viewed
as a natural Unix machine. So when we were working on the 386 definition we
wanted it to have as one of its attributes being able to run Unix well.
So that’s one of the things that influenced us in terms of wanting to have a
way to run the 386 as a flat 32-bit machine, and that’s one of the things
that led to all the angst in the definition process about compatibility versus
a flat 32bit machine and how they would coexist.
（省略されました・・全てを読むにはここを押してください）
- 722 名前：ナイコンさん ：2013/06/08(土) 21:01:28.94
- [Jarrett:] So that shapes up as a key challenge architecturally;
how did you address that?
アーキテクチャ的に挑戦すべき鍵となる点が形作られたわけですが、どう取扱いましたか?
(p8)
[Crawford:] In fact that was one of the most difficult architectural issues
that I had to wrestle with: how to keep that compatibility with the
segmentation yet provide this thing and I know we went through endless
iterations and had a lot of advice from many people.
In the end the thing that worked was inventing a fictional address space in
between the programmer’s virtual address space and the physical address that
you go to memory with; in fact we had to invent a new name for it,
so we called it the “linear address space”
We kept the segments but we provided the ability to have a segment that was
four gigabytes in size and that let the workstation guys and the Unix people
address this four gigabyte flat address space basically by setting up one
（省略されました・・全てを読むにはここを押してください）
- 723 名前：ナイコンさん ：2013/06/08(土) 21:03:01.49
- [Slager:] Of course there’s controversy about all of this and, you know,
it’s incredible and one thing that I remember well is that the architect of
the 8086, one of the two architects, Steve Morris, who started the whole X86
phenomenon… he was bitterly opposed to the segmentation model that was
installed in the 286. When the 386 turn came he was very active-- he was still
at Intel in software somewhere-- and he was very much opposed to the segmentation
model because of the two-part pointers. In fact he called it software poison.
もちろん、知っての通りこれら全部について議論はありました。私がよく覚えてるのは
8086を設計した二人の開発者のうちの一人、Steve Morris つまりx86現象を始めた張本人
である彼が、286に組み込まれたセグメンテーション・モデルに厳しく反対したことです。
彼はソフトウェアか何かの部門でまだインテルに在籍してましたが、386の段階が来ても
とても積極的で、ポインタが2パートになるという理由で、セグメンテーションにとても
反対でした。実際彼はそれを、ソフトの害毒と呼んでました。
This was the environment that John had to work in and he did come up with a
（省略されました・・全てを読むにはここを押してください）
- 724 名前：ナイコンさん ：2013/06/08(土) 21:05:22.82
- [Leukhardt:] Now in some ways we’re getting ahead of ourselves because we got
to the solution that included segmentation plus a flat address space, sort of
the “have it your way” approach after we made the decision that we had to
build a fully compatible machine that is an object code compatible 386, and
that took a long time to decide. In retrospect that seems like a completely
obvious decision but we wrestled with that decision for months and it was a
tough decision-making process.
オブジェクトコード完全互換として386を作らねばならないと決めた後に、セグメントと
フラットアドレスの両方を含み、いわば「あなたの好きな方法でどうぞ」のアプローチを
とる解決策を得て、やっと私達は前を向くことになります(?)。この決断には長い時間が
かかりました。思い返してみるとまったく明白な決断に思えるのですが、当時の私達には
何ヶ月も要する大変な意思決定プロセスでした。
- 725 名前：ナイコンさん ：2013/06/08(土) 21:06:08.94
- [Jarrett:] So John, you came up with this new approach that would accommodate
both segmentation and paging. Was there any kind of a performance price that
you paid as a result of this?
そうして John, あなたはセグメントとページングを両方内蔵する新しいアプローチに
辿り着いたわけですが、その結果、何かパフォーマンスの劣化がありませんでしたか?
[Crawford:] That’s an interesting question; in fact it was obviously a big
concern because we were putting in two translation steps.
Of course it’s a critical path on any computer, and that was a big concern
all through the internals of the chip and even the BUS definition that was a
careful concern. But the advantage was, I think it was mentioned before, we
got the best of both worlds: we had segments for compatibility and paging for
a flat address base; that was pretty much everybody.
いい質問です。実際、二段階の変換ステップを入れるは明らかに心配でした。もちろん
（省略されました・・全てを読むにはここを押してください）
- 726 名前：ナイコンさん ：2013/06/08(土) 21:07:34.97
- [Jarrett:] Now internally, did everybody buy into this immediately or was
there some debate on this approach?
社内的には全員がすぐに賛成したのですか、それともこの方法に何か議論がありましたか?
[Crawford:] Well, I think that came at some point in 1982, but before that
there were many proposals, obviously which didn’t survive, that didn’t solve
the problem as completely. At some point there was a decision taken to go with
my architecture as opposed to the Bob Childs architecture. As I remember, a key
part of that was involved the software compatibility question and how efficiently
we needed to run old software, and whether there would be a mode bit and
basically have two machines in one or something more tightly integrated.
ええ、これは1982年のどこかだと思いますが、それ以前は多くの提案がありました。
明らかにどれも生き残りませんでした。完全には問題を解決できなかったからです。
ある時点で Bob Childsのアーキテクチャでなく、私の案で行く決定がなされました。
（省略されました・・全てを読むにはここを押してください）
- 727 名前：ナイコンさん ：2013/06/08(土) 21:09:58.30
- [Crawford:] (続き)
I guess in addition I got half credit for the register extension because I was
able to generalize the registers. On the 8086 they were quite specialized and
the software people hated that too. One of the things I was able to get into
the architecture was to allow any register to be used to address memory as a
base or an index register, and was even able to squeeze in a scale factor for
the index.
さらに、レジスタを汎用化できたことで半分は面目を保てたと思います。8086では
とても特殊化されていて、これもソフトウェアの人々から嫌われていました。
私がアーキテクチャに組み込めたことの一つは、どのレジスタもアドレスのベースや
インデックスとして使え、さらにスケールファクタも入れられる点です。
【8bit機】CRTC,VDP,ALU,メモリマップ,MMU 専スレ
http://ikura.2ch.net/test/read.cgi/i4004/1221375066/290-
（省略されました・・全てを読むにはここを押してください）
- 728 名前：ナイコンさん ：2013/06/08(土) 22:49:52.41
- いやはやあっぱれ、あっぱれじゃ
楽しく読ませてもらいました
- 729 名前：ナイコンさん ：2013/06/23(日) 16:45:19.61
- インテルは２８６出した後でも「モトローラに追いつかなきゃ！」って頑張ってたんだな
- 730 名前：ナイコンさん ：2013/06/23(日) 17:17:02.49
- 80286と同時期で68020だからね、そりゃ頑張るしかないだろ。
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