Article View: alt.folklore.computers
Article #618453Re: S/360 addressing, not Honeywell 200
From: Charles Richmond
Date: Sun, 28 Jan 2018 18:29
Date: Sun, 28 Jan 2018 18:29
35 lines
3412 bytes
3412 bytes
On 1/27/2018 7:22 PM, Charlie Gibbs wrote: > On 2018-01-28, Dan Espen <dan1...@gmail.com> wrote: > >> John Levine <jo...@taugh.com> writes: >> >>> In article <b204534e-f56c-4b29...@googlegroups.com>, >>> >>>> Memory addressing was a big issue in the original concept of >>>> System/360. Small machines had simple addresses which saved >>>> memory, big machines had more complex addresses. Providing space >>>> for a large address was wasteful in a small machine, most >>>> S/360 users were getting small ones. As a compromise, IBM came >>>> up with the base+displacement method. >>> >>> All 360s other than the /20 used the same addressing, full 24 bit >>> addresses, instructions used base register plus 12 bit displacement >>> sometimes plus index register. Base register 0 meant direct >>> addressing with the 12 bit displacement, but as far as I know that was >>> used only in little bits of startup and trap handler code, not in >>> applications. >> >> MVS applications often get system information >> by using an address at a fixed low storage location (CVT at 16). > > It also lets you use Load Address to load a constant from 0 to > 4095 inclusive into a register (although if you're setting the > register to zero it's faster to subtract it from itself). > How does that compare with the time for exclusive-oring the resister with itself??? On the Intel 8080, that was the fastest way to zero the accumulator... -- numerist at aquaporin4 dot com
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X-Received: by 10.200.40.246 with SMTP id j51mr15292712qtj.34.1517164152908; Sun, 28 Jan 2018 10:29:12 -0800 (PST) X-BeenThere: alt.folklore.computers@googlegroups.com Received: by 10.55.195.202 with SMTP id r71ls477251qkl.13.gmail; Sun, 28 Jan 2018 10:29:12 -0800 (PST) X-Received: by 10.55.101.13 with SMTP id z13mr14883503qkb.50.1517164152269; Sun, 28 Jan 2018 10:29:12 -0800 (PST) Path: mbox-mo1.pugleaf.net!e39ni779qtk.1!nntp.google.com!peer02.iad!feed-me.highwinds-media.com!peer02.am4!peer.am4.highwinds-media.com!news.highwinds-media.com!news.roellig-ltd.de!open-news-network.org!feeder.erje.net!1.eu.feeder.erje.net!eternal-september.org!feeder.eternal-september.org!reader02.eternal-september.org!.POSTED!not-for-mail From: Charles Richmond <nume...@aquaporin4.com> Newsgroups: alt.folklore.computers Subject: Re: S/360 addressing, not Honeywell 200 Date: Sun, 28 Jan 2018 12:29:18 -0600 Organization: A noiseless patient Spider Lines: 35 Message-ID: <p4l4pn$17i$1@dont-email.me> References: <65g3r9$8gg@bgtnsc03.worldnet.att.net> <p4cn29$fhm$1@dont-email.me> <p4d45k$f8e$1@dont-email.me> <b204534e-f56c-4b29-a177-dd66c2410b6d@googlegroups.com> <p4j0er$2im8$1@gal.iecc.com> <p4j5vb$u75$3@dont-email.me> <p4j8ki0ho2@news6.newsguy.com> Reply-To: nume...@aquaporin4.com Mime-Version: 1.0 Injection-Date: Sun, 28 Jan 2018 18:29:11 -0000 (UTC) Injection-Info: reader02.eternal-september.org; posting-host="a24c86cd296078f24f2e755cab91d396"; logging-data="1266"; mail-complaints-to="ab...@eternal-september.org"; posting-account="U2FsdGVkX1/iic5HWzKgniS3ZdQ+p66tKa3yHw3jhbI=" User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.5.2 In-Reply-To: <p4j8ki0ho2@news6.newsguy.com> Cancel-Lock: sha1:geDQyAjuClegR1sroO1bzbeV/1I= X-Received-Body-CRC: 2739940999 X-Received-Bytes: 3014 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit