I never said or tried to imply that it anything more than an architectural description. But I was saying S/360 was publically described before that in the principles of operation by IBM. At that point, you were fine to clone it.

In fact, this is what put Ken O at Cal Data out of business a few years later when he cloned the PDP-11 ISA (from the processor handbook descriptions) and cloned the Unibus which had only been described in schematics. Thus Ken was careful later to only make bus repeaters/Caches and the like at his new firm Able Computer (although he built, but I do not believe he ever actually sold, a M68010 on a 22-bit QBUS at one point).

As it turns out, under those rules, its possible Amdahl might have been in violation of IBM's IP, but again the difference was that the amount of money he was taking from IBM was small, and IBM was (correctly worried) about the Justice Dept. I fact a few years later IBM was enjoined for monopolistic practices (1969 and vacated without merit in 1980: https://web.archive.org/web/20100408174629/http://www.hagley.lib.de.us/library/collections/manuscripts/findingaids/ibmantitrustpart2.ACC1980.htm).

On Mon, Nov 18, 2019 at 1:45 PM Bakul Shah <bakul@bitblocks.com> wrote:

Are you guys talking about “A formal description of System/360” by Falkoff, Iverson and Sussenguth? It uses an APL like notation but not exactly a S/360 emulator in APL! Much more concise than the S/360 POP.

http://www.cs.trinity.edu/~jhowland/class.files.cs2321.html/falkoff.pdf

On Nov 18, 2019, at 8:43 AM, Clem Cole <clemc@ccc.com> wrote:

On Sun, Nov 17, 2019 at 12:14 AM Dave Horsfall <dave@horsfall.org> wrote:
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...

The cat was already out and poking around with the publishing of: IBM 360 Principles of Operation, DOC A22-6821-0. The APL version of spec just gave it more area to roam.
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