Hitachi has also entered an agreement to develop future versions of IBM's PowerPC microprocessors, which are used in both IBM's pSeries (formerly RS/6000) and iSeries (AS/400) systems.
The deal gives IBM a new channel for its Unix platforms, especially in Japan, and will further its aims to popularise Linux through the Linux-friendly AIX operating system.
IBM will also be able to reduce the cost of R&D for the PowerPC line at a time when it needs to make savings in its $5bn (£3.5bn) total R&D budget to find the $1bn it has committed to spend on Linux developments.
The agreement covers the development of components, including semiconductors and cache memory parts, as well as complete servers. Neither company has put a value on the deal or disclosed whether any money has changed hands.