
T3, which hails from Florida and bills itself as "the other mainframe company " launched a similar complaint with the US Department Of Justice in 2007.
In that filing, the company alleges that IBM unfairly used its dominance over the mainframe software market to push its hardware.
"Because 85 per cent of the mainframe users have adopted IBM's operating systems, thousands of companies have invested over a trillion dollars in IBM-compatible software and hardware," reads the filing.
"Those users (who reasonably expected that IBM would continue fairly and reasonably offering its operating system and technical support for use on competing hardware) are not "locked in" to using IBM-compatible hardware and software."
The complaint alleges that beginning in 2002, Big Blue began to push T3 out of the market by making it difficult for customers to install IBM software on T3 mainframe hardware.
IBM had previously faced a similar complaint from Platform Solutions, though the case was snuffed out when IBM acquired Platform Solutions last summer and both sides agreed to drop legal claims.