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Path: ...!news.mixmin.net!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail From: Lawrence D'Oliveiro <ldo@nz.invalid> Newsgroups: comp.arch Subject: Re: ancient OS history, ARM is sort of channeling the IBM 360 Date: Sun, 30 Jun 2024 07:22:23 -0000 (UTC) Organization: A noiseless patient Spider Lines: 21 Message-ID: <v5r13f$dn62$2@dont-email.me> References: <s7r87j1c3u6mim0db3ccbdvknvtjr4anu3@4ax.com> <e4f7278a5ff4e0b488306ae43aac8135@www.novabbs.org> <v5nbfo$3hdrc$1@dont-email.me> <v5o6jr$37jie$1@dont-email.me> <v5pjcc$25j5$1@gal.iecc.com> <v5q6qm$5fhe$1@dont-email.me> <v5qn67$c1dr$1@dont-email.me> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Injection-Date: Sun, 30 Jun 2024 09:22:24 +0200 (CEST) Injection-Info: dont-email.me; posting-host="4341965ad4e2fb75a1b93d496a5627b7"; logging-data="449730"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX19J3bDHr3r8YZ+zl+JbVGNh" User-Agent: Pan/0.158 (Avdiivka; ) Cancel-Lock: sha1:oIjJ1ONGI36e+OjLPAyhgNaeruE= Bytes: 2089 On Sun, 30 Jun 2024 04:33:11 -0000 (UTC), Stephen Fuld wrote: > Lawrence D'Oliveiro wrote: > >> By the 1970s, CPU/RAM speeds had improved to the >> point where copying records a few hundred bytes at a time between >> buffers was not the performance bottleneck; disk I/O was. > > Yes, but given multiprogramming, even in the 1970s, you would typically > have several batch programs running at the same time, so during waits > for I/O, another program could use the CPU. But using the CPU to move > records meant it couldn't be doing anything else at the same time. Scraping the bottom of the barrel, much? Work out the numbers. The CPU time necessary to copy a single record is most likely a small fraction of the time it takes to service an I/O interrupt. And this is not taking into account the fact that I/O interrupts run at a higher priority than user-level tasks like copying buffers, anyway.