From mboxrd@z Thu Jan 1 00:00:00 1970 From: dave at horsfall.org (Dave Horsfall) Date: Sat, 16 Nov 2019 09:42:47 +1100 (EST) Subject: [COFF] In Memoriam: Jay W. Forrester, happy birthday Gene Amdahl, and LSD In-Reply-To: <99f46273-e2a4-4a82-f827-8c00fb48f633@kilonet.net> References: <99f46273-e2a4-4a82-f827-8c00fb48f633@kilonet.net> Message-ID: On Fri, 15 Nov 2019, Arthur Krewat wrote: > How did Amdahl get away with making 360 clones? I would have thought > that IBM would have crushed his bones into dust. Clones in the way that they were able to run OS/360; that's about all that I can remember. Hitachi also came out with a clone, as did no doubt many other manufacturers; after all, the instruction set was public knowledge... I dimly recall that some opcodes had undocumented side-effects, so in theory (and likely in practice) OS/360 could detect whether it was running on a clone, and "fail to proceed" (in Rolls Royce terms). My favourite /360 instruction on our customised system was "SVC 254" which got you supervisor mode (long story, depending upon the statute of limitations). The operators and I had a love-hate relationship i.e. they loved to hate me :-) Soon after I got a job with them i.e. better to keep me inside the tent than out... -- Dave