I hate it when I miss important anniversaries. The 360 was announced on April 7, 1964. Building the System/360 Mainframe Nearly Destroyed IBM.
(The image is an IBM System/360 Model 20 CPU with front panels removed, with IBM 2560 MFCM (Multi-Function Card Machine) Ben Franske [CC BY 2.5 (https://creativecommons.org/licenses/by/2.5)%5D, via Wikimedia Commons. Click for a larger view.)
Before the 360, computers were one-off. If you wanted to upgrade to a larger system, every piece of software had to be rewritten. Upgrading to a newer processor required buying new disk and tape drives, as well as printers. To put it bluntly…
By the end of the 1950s, computer users faced a seemingly intractable problem. Had it not been solved, it would have prevented computers from becoming widespread, and any thoughts of living in an Information Age would have been fiction.
So they pretty much bet the company, and embarked on a path that leads to where we are today, where you can add new disk-drives to old computers, where you can upgrade your graphics processor, or add more ports or a new printer by mostly just plugging it in, or you can buy a new computer and use your old mouse, keyboard, monitor and printer.
Their report called for five compatible computers, labeled processors (defined as the computer, its memory, and channels to connect to peripheral equipment). The software and peripherals for one processor were to work with all other processors. The plan called for using standard hardware and software interfaces between computers and peripherals, such as between disk drives and tape drives connecting to computers, so that the peripherals did not have to be swapped out when a new processor was installed. The recommendations became the basis for the System/360.
Principles of Operations, or Principles of Ops, – which grew out of that original report, and spelled out everything – was a standard volume on every system-programmer’s, DBA’s, and other’s desks. The last time I can clearly remember having a copy on my desk was in 1997. (That was when I was pushed into management…tricked, might be a better description of what happened…)
In short, the IBM 360 was the first computer you could upgrade. And it was just what people needed.
In the first month following the S/360 announcement, customers worldwide ordered over 100,000 systems. To put that number in perspective, in that same year in the United Kingdom, all of Western Europe, the United States, and Japan, there were slightly more than 20,000 computers of any kind installed.
Say it again. The order backlog was nearly 500 percent of the then worldwide-installed-base.
Anyway, anyone interested in tech might want to look at that bit of history. (Hat tip to the Chicago Boyz.)