- Posted April 27, 2014, 9 a.m. - 6 years, 8 months ago
42 years ago today IBM installed the first IBM 370/135 mainframe computer, just one of the models included in the S370 series which IBM ran for nearly 20 years, achieving significant market share in the process.
Both developed and manufactured by IBM in the UK, the IBM 370/135 and 145 were the mid to lower end of the mainframe range, following on from the high end machines released in 1970 which superseded the System/360 family of computers.
Key features of the IBM 370/135 included:
- 240,000 bytes of main memory capacity, four times greater than the S360/30 with Microcode reloadable control storage (RCS) supplementing this with a further 24,000 bytes. The option was also available to increase the RCS to 36,000 or 48,000 bytes if required.
- Monolithic circuitry that increased internal operating speeds, exceeding those of the S360/30 over four fold, resulting in speeds of 275 to 1,430 nanoseconds for one microinstruction completion.
- ICAs – Integrated Communications Attachments allowing terminals to be linked to the central processor via up to 8 communication lines, without the need for separate control units. The 370/135 also offered compatibility with virtually all of IBM’s terminal devices.
- Expanded Channel capacity that enabled block multiplexing and increased system throughput.
- Advanced self-checking features and console critical points status displays.
- Increased disk storage, with optional integrated file adapter together with additional disk storage features were available, removing the need for separate disk control units.
- Backward compatibility with the S/360 models, offered as standard with all 370/- models allowing customers easy migration to the 370/- mainframes.
- OS/DOS program compatibility support.
With a starting price of nearly $500,000 ranging to over $1,000,000, rentals also proved popular with monthly contracts upwards of $10,000. Later additions to the 370/- portfolio saw the inclusion of full virtual memory before the range was finally superseded in the 1990’s by the IBM System/390.
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