Were the mainframe a person, it would now start thinking about retirement: the mighty corporate computer was born in the 1950s. But mainframes remain at the core of the IT systems of many banks and other big organisations. Analysts estimate that these machines, with related hardware, software and services, provide a quarter of IBM’s revenues and 35% of its profits. So it is easy to understand why on Tuesday evening Big Blue unveiled the z13, a new model intended to make its flagship product fit for the age of cloud and mobile computing. The oldest of “old tech” companies has been struggling to keep up with younger upstarts. Will it succeed? A partial answer will come next Tuesday, when IBM reports fourth-quarter results and is expected to announce some organisational changes, such as separate units to house its cloud, e-commerce and other businesses.