From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.5-pre1 (2020-06-20) on ip-172-31-74-118.ec2.internal X-Spam-Level: X-Spam-Status: No, score=-1.9 required=3.0 tests=BAYES_00 autolearn=ham autolearn_force=no version=3.4.5-pre1 Path: eternal-september.org!reader02.eternal-september.org!feeder.eternal-september.org!gandalf.srv.welterde.de!news.jacob-sparre.dk!franka.jacob-sparre.dk!pnx.dk!.POSTED.rrsoftware.com!not-for-mail From: "Randy Brukardt" Newsgroups: comp.lang.ada Subject: Re: is there a version of unix written in Ada Date: Wed, 30 Sep 2020 17:42:01 -0500 Organization: JSA Research & Innovation Message-ID: References: <00cd3aaa-d518-43a2-b321-58d6fae70aebo@googlegroups.com> <57eb7a65-51ea-4624-b9dc-9c4dda0fee59n@googlegroups.com> <5f70fd3b$0$13541$426a74cc@news.free.fr> <87wo0d3iac.fsf@nightsong.com> <87sgb02l7b.fsf@nightsong.com> <875z7vyy1u.fsf@nightsong.com> <87wo0bkns3.fsf@nightsong.com> Injection-Date: Wed, 30 Sep 2020 22:42:07 -0000 (UTC) Injection-Info: franka.jacob-sparre.dk; posting-host="rrsoftware.com:24.196.82.226"; logging-data="13262"; mail-complaints-to="news@jacob-sparre.dk" X-Priority: 3 X-MSMail-Priority: Normal X-Newsreader: Microsoft Outlook Express 6.00.2900.5931 X-RFC2646: Format=Flowed; Response X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.7246 Xref: reader02.eternal-september.org comp.lang.ada:60347 List-Id: "Dmitry A. Kazakov" wrote in message news:rl2rqt$jdq$1@gioia.aioe.org... > On 30/09/2020 22:33, Paul Rubin wrote: >> "Dmitry A. Kazakov" writes: >>> I want an OS protecting from compilers I do not trust without >>> performance loss. >> >> That is not possible. Traditional OS's use memory protection hardware >> for that, but that hardware introduces performance loss. > > I do not see why loss must be any bigger that other means of > synchronization. Synchronization is rather expensive, since it causes issues with prefetch and caches and pretty much everything else that improves performance. ... > P.S. Surely MS-DOS coordinated auxiliary processors, there exited lots of > expansion cards with processors on them in MS-DOS times. I suppose, that was done with device drivers and the like, below anything visible. I don't remember every worrying about what was happening on cards, anymore than one does nowdays on Windows or Linux. > P.P.S. In MS-DOS processes were coordinated using glorious INT 21h. (:-)) Since there wasn't any extra processing (no cores back then), anything working like a process was a hack. Janus/Ada used (and still uses) cooperative multitasking to give the appearance of multiple processes, but no such thing was actually happening. Given that MS-DOS itself wasn't re-enterant, it was too risky to use any sort of conventional interrupt-driven tasking. (Some people did it anyway, by trusting various undocumented hacks; there even was a famous book about those - which came out way too late to influnce the Janus/Ada design.) Randy.