Path: ...!news.iecc.com!.POSTED.news.iecc.com!not-for-mail From: John Levine Newsgroups: comp.arch Subject: Re: architecture, The Design of Design Date: Thu, 9 May 2024 02:10:17 -0000 (UTC) Organization: Taughannock Networks Message-ID: References: <86a5l2tnyk.fsf@linuxsc.com> <20240507115433.000049ce@yahoo.com> <865xvou00p.fsf@linuxsc.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Injection-Date: Thu, 9 May 2024 02:10:17 -0000 (UTC) Injection-Info: gal.iecc.com; posting-host="news.iecc.com:2001:470:1f07:1126:0:676f:7373:6970"; logging-data="9319"; mail-complaints-to="abuse@iecc.com" In-Reply-To: <86a5l2tnyk.fsf@linuxsc.com> <20240507115433.000049ce@yahoo.com> <865xvou00p.fsf@linuxsc.com> Cleverness: some X-Newsreader: trn 4.0-test77 (Sep 1, 2010) Originator: johnl@iecc.com (John Levine) Bytes: 2132 Lines: 25 According to Tim Rentsch : >> My impression is that until S/360 there was no such thing as different >> by 100% SW compatible models. > >I think a counterexample is the LGP-30 (1956) and its successor >the LGP-21 (1963). They were pretty close but it says on the intertubes that the -30 put memory words 9 apart on the drum and the -21 put them 18 apart, which I presume means that you would need to arrange your data differently to get good performance. >Another example may be the IBM 709 and IBM 7090, both done in the 1950s. They were pretty similar but the 7090 had a more complex channel and new instructions to manage it. There was a trap mode that caught the old I/O instructions they used to run 704 or 709 coe on a 7090 but of course not vice versa. Compare that to S/360 where every model had the same channel interface, the same I/O instructions, and the same I/O interrupts. -- Regards, John Levine, johnl@taugh.com, Primary Perpetrator of "The Internet for Dummies", Please consider the environment before reading this e-mail. https://jl.ly