A mainframe hardware vendor based in the US has today filed an antitrust complaint against IBM to the European Commission.

T3 Technologies alleges that IBM’s policy of allowing customers to run its mainframe operating system only on the hardware it makes itself is in breach of EU competition law.

IBM used to allow other mainframe manufacturers Hitachi and Amdahl to load its range of mainframe operating systems on their hardware. However, these companies have since backed out of the mainframe business.

Critics argue this leaves IBM with an effective monopoly in mainframes, but the company itself points out that there are numerous alternatives in high-power computing.

The EC began investigating IBM’s mainframe practices in 2007 following a similar complaint from mainframe Platform Solutions Inc (PSI). That complaint was resolved, however, when IBM acquired PSI. T3’s complaint is expected to revive the EC investigation.