modified on 2 October 2015 at 22:16

IBM System/36


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The IBM System/36 is a midrange minicomputer that was introduced in 1983 and discontinued in 2000. It is a direct ancestor to the current popular AS/400 computers. It was targeted at business customers, and was very good at things like database management, accounting, and general business automation tasks.

It is powered by two 16-bit processors, the CSP or Control Storage Processor, and the MSP or Main Storage Processor. These are clocked at 4MHz and 1MHz, respectively. The system communicates with peripherals via IBM's Twinax cabling, which is a type of network bus. Terminals, printers, and other peripherals connected to Twinax ports on the system unit, and the operating system (called SSP, for System Support Program) could automatically identify and configure any connected peripherals at IPL (boot) time. This was highly advanced functionality for the early 1980s.

My IBM System/36 model 5360.

The front of the system is clean and relatively featureless. Note that the control panel has a cover that hides most of the lights and control switches, contributing to a clean, non-intimidating appearance. Remember, this mid-range minicomputer was intended for office use by relatively nontechnical people in an era during which many people had never seen a computer.

One very unusual feature of the System/36 model 5360 is the floppy disk changer. It holds two cartridges, called magazines, each of which holds ten eight-inch floppy disks. A robotic mechanism selects disks and inserts them into the disk drive under program control.

This particular System/36 was acquired in the summer of 2008. The story of its retrieval, including pictures, can be found here. It has 128KB of main storage for the MSP (RAM is called "storage" in IBM parlance) and 64KB of control storage for the CSP. The system has two type 21ED hard drives, each with a capacity of 30MB. The system is also equipped with a type 5224 line printer, which I finally repaired in October of 2015.