When IBM rolled out its IBM System/360 back in 1964, these big metal cabinets housing primitive circuitry and endless spools of magnetic tape were revolutionary pieces of technology, hurtling the banks into the future.

50 years later, the magnetic tape is long gone but 92 of the world’s top 100 banks still rely on IBM mainframes, according to the company. The majority of them are in retail banks, but a “significant number” of investment banks are also still using the technology, according to Keith Bear, vice president, financial markets at IBM. Their clients’ ranks include Morgan Stanley, HSBC and UBS.