From mboxrd@z Thu Jan 1 00:00:00 1970 From: dave at horsfall.org (Dave Horsfall) Date: Sun, 17 Nov 2019 16:14:10 +1100 (EST) Subject: [COFF] In Memoriam: Jay W. Forrester, happy birthday Gene Amdahl, and LSD In-Reply-To: <20191116072354.GA74610@server.rulingia.com> References: <99f46273-e2a4-4a82-f827-8c00fb48f633@kilonet.net> <20191116072354.GA74610@server.rulingia.com> Message-ID: On Sat, 16 Nov 2019, Peter Jeremy wrote: > More than just the instruction set - IBM published a formal description > of the S/360 (in APL in the IBM Systems Journal issue that announced the > S/360). The S/360 was (I believe) the first case where a company > announced a computer architecture (rather than an implementation) and > implementations were expected to precisely comply with the architecture > (no more finding undocumented instructions and side-effects and writing > code that depended on them). This meant that clone makers could build a > clone that accurately emulated a S/360. Ah, I'd forgotten about the APL documentation; thanks! Talk about giving away the keys to the kingdom: Amdahl, Fujitsu, Hitachi... > AFAIR, the only "implementation defined" instruction was DIAGNOSE, > OS/360 could presumably tell what it was running on by checking > particular DIAGNOSE function. (VM/370 was paravirtualised and used > DIAGNOSE to communicate with the hypervisor - CP). Another point I had forgotten :-( Yep, the DIAG instruction was utterly implementation-dependent, and thus OS/360 could tell whether it was running on a clone or not. Cut me some slack; I turned 67 last month :-( > In the early PC era, it was not uncommon for applications to verify they > were running on a genuine IBM PC by looking for the copyright notice in > the BIOS - which clone makers countered by placing a "not" before an > equivalent copyright notice. I remember the days of the "grey imports" (or "gray" for the Americans); if it ran Flight Simulator and not labelled "IBM" then it was technically illegal; shortly afterwards if it did *not* run FS then nobody would buy it :-) How things change... -- Dave