Btw the way diagnose instruction worked was it used jumps into the microcode. Very cool. I still have a TILT deck that is a 4 card program written using mostly 360/67 diagnose instructions. FYI. The “DAT” (data address translation-aka the vm unit) was a separate box attached to the side of the CPU which was filled with incandescent lamps. Also remember that the console bell on the 360 was a large fire alarm style bell This program spelled TILT on the lights of the DAT box and sent a bell char to the console every .5 sec like a large pinball machine. Sadly it was a standalone program that we could only run at night but very cool none the less. Clem On Sat, Nov 16, 2019 at 2:24 AM Peter Jeremy wrote: > On 2019-Nov-16 09:42:47 +1100, Dave Horsfall wrote: > >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... > > 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. > > >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). > > 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). > > 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. > > -- > Peter Jeremy > _______________________________________________ > COFF mailing list > COFF at minnie.tuhs.org > https://minnie.tuhs.org/cgi-bin/mailman/listinfo/coff > -- Sent from a handheld expect more typos than usual -------------- next part -------------- An HTML attachment was scrubbed... URL: