[COFF] In Memoriam: Jay W. Forrester, happy birthday Gene Amdahl, and LSD

[clemc at ccc.com (Clem Cole)]

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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 <peter at rulingia.com> wrote:

> On 2019-Nov-16 09:42:47 +1100, Dave Horsfall <dave at horsfall.org> 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
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-- 
Sent from a handheld expect more typos than usual
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