Happy birthday, System 360

From here:

The IBM mainframe is celebrating its 50th anniversary.IBM360-40-bw

The first System 360 mainframe was unveiled on 7 April 1964 and its arrival marked a break with all general purpose computers that came before.

The machines made it possible to upgrade the processors but still keep using the same code and peripherals from earlier models.

I started working on a 360 model 40 two years after its introduction in 1966; I probably would have retired by now if someone hadn’t sued me but, alas, I toil on. What is extraordinary is that the z series mainframes that I now work on have essentially the same instruction set – admittedly with embellishments – as the antique 360. Writing a mainframe assembler program today isn’t too different from when I started in 1966.

The illustration above is a 360 model 40. The one I programmed had, as I recall, 8k of core memory (the early version of RAM: little magnetic rings threaded on wires). The operating system was 8k BOS, a non-multitasking OS which was not even able to spool print output. It was not much later that we upgraded to a luxuriant 16k of core and DOS which could not only spool print but had foreground and background jobs: a very primitive form of multi-tasking.

Here is a front panel of a 360/40. The big red knob disconnected power from everything; we never touched that. The lights showed actual bit values in core and the switches allowed us to dynamically change bits if things were not running as they should.

IBM 360-40The 2311disk drives we used held 7.25 megabytes; they were big boxes that shook when in use and, when broken, would occasionally leak hydraulic oil onto the floor. I miss those days.

IBM_2311disk

Then there were the punched cards whose inconvenience was only slightly mitigated by the pool of girls operating the card punches.

punch_card_do_1