IBM System/360 Principles of Operation (1964) [pdf]

I did a tour of duty as a CPU logic designer at Amdahl. The POO was my bible, although it was the 370 version in those days. The thing to remember about ISA specs like this is that they are works of fiction. The contract goes: “If you programmers are willing to pretend this is how the machines work, we will build a machine that pretends to work that way.” That concept is the key innovation of the 360 system architecture, attributed to Gene Amdahl.

After leaving Amdahl I worked for a while in Electronic Design Automation. One year at the IEEE Design Automation Conference I met a random person at a happy hour who was an ex-IBM OS programmer. He said that he once spent a year rewriting a part of the OS to use a particular instruction entirely because “Amdahl didn’t have it yet.” Says I: “When was this?” ... “Ah, at that time part of my job was adding that instruction to the Amdahl CPU.”

The conversation felt like an old Mad Magazine “Spy vs. Spy” cartoon. We were both bemused.

In 1970, I actually got paid a salary to write applications in this Assembler language. Abjectly inefficient, but what a blast!

When IBM introduced the AP (attached processor) and MP (multi-processor) systems, they had to add instructions that were guaranteed to be atomic since both processors had uniform access to main memory. Interestingly enough, they only added two instructions (compare and swap, compare double and swap) to support these configurations.

(I think there might have been one or two other supervisor mode-instructions, but there were weirdos like "stop the other processor", for example).

I remember reading a similar document for my shop's IBM 4381.

When I started mainframe programming, I was given a pocket-sized 'yellow card' that listed all the machine instructions and arguments. It was invaluable for dump-reading.

My co-workers (who were all older when I started) had similar cards, except in different colors. There were white, pink and green cards, too. You could tell when somebody started programming by the color of their card.

I kept mine, still have it.

Coincidentally, I finished reading "IBM's 360 and Early 370 Systems" earlier today. I highly recommend it and its predecessor, "IBM's Early Computers" from the MIT press. The business aspect is there, of course, but it's really about the development of the machines themselves, down to how they developed the transistors they used along with who did it.

The Adolescence of P-1 was set on IBM System/360 mainframes.

https://en.wikipedia.org/wiki/The_Adolescence_of_P-1

>Reception

>BYTE criticized The Adolescence of P-1 for what it stated were unrealistic expectations for an artificial intelligence running on 1970s IBM mainframes. It suggested that the author could have set the novel in the 1990s and use fictional future IBM computers to make the plot more plausible.

https://archive.org/stream/byte-magazine-1981-09/BYTE_Vol_06...

Heh - had to go look up storage protect, aka 'red light errors' . Kept getting in trouble in the beginning of my career when I didn't realize snooping about lit up lights on the front panel . :-)

That's the easy one. z/Arch is way more intricate. As noted in my moniker, you can do fun stuff with BXLE,as described in the "Difficult Code" section on FINCH (aka program fetching) in an OS/360 PLM (Program Logic Manual).

This was my bible for many years. We called it POOP (Principles Of OPeration. I loved assembler on the 360 and the 370. I learned Assembly Language by cross listing my COBOL programs and using POOP to find out what the op codes meant.

I dare say these boys will find the manual rather handy.

https://ibms360.co.uk/

Fair warning: this is not an introduction.

Anybody got a year for this?