IBM has unveiled a mainframe computer it hopes will help head off competition from lower cost PC-based servers. It said the zEnterprise EC12 had cost $1bn (£633m) to develop, producing a machine with processing cores 25% more powerful than earlier models. The re-designed machine also had better security and data-analytics tools than older models, said IBM. The launch comes at a time when, analysts say, the mainframe market is experiencing a long-term decline. IBM is by far the biggest seller of mainframes and the machines remain popular with big banks and other organisations that use the large computers for their heavy data-processing needs. Prices for a basic mainframe, which are based around IBM’s own silicon chips, start at about $1m (£633,000).