IBM 370/135 – Anniversary of the First Installation
The 27th April 1972 saw the first installation of an IBM 370/135 mainframe computer take place in Britain, following IBM’s announcement just under a year earlier in March 1971 that their System 370/135 had not only been designed in Britain at the IBM Development Centre based in Hursley, but that the manufacture of these machines would also take place in the UK at IBM’s plant in Havant to fulfil requirements of the European, African and Near East markets.
Following on from the success of IBM’s new high end 370/155, 165 and 195 machines, the 370/135 was designed with the low to mid-range market in mind. With four main storage sizes available, it had the capability to offer four times the memory of the S360/30 with 240,000 bytes, alongside significant increases in internal operating speeds when compared to other models achieved through the use of monolithic circuitry. The 370/135 offered greater flexibility for customers and cost savings with expanded channel capacity allowing block multiplexing and subsequent increased throughput, in addition increased disk storage capability and efficiency via the IBM 3330 system was also a feature.
Optional disk storage control features and integrated communications attachments allowing for linking up to 8 terminals to the central processor were also on offer adding to the 370/135’s multiprogramming and teleprocessing capability. As with the previous 370/- models, S/360 backward compatibility facilitated easy migration to the new machines, with users able to run S/360 applications without the need to reprogram. The 370/135 also included program support in the form of OS/DOS compatibility, enabling users to execute those programs written for DOS under OS. Advanced self-checking features were incorporated including CPU retry, with console face displays also indicating critical points status.
The price tag for these machines started at $475,000 up to £1,068,000 and they were available to rent for a monthly fee upwards of $10,000. The 370/135 was withdrawn by IBM in October 1979, with additional 370/- models continuing to be added to the range throughout the 1970’s and 1980’s.