Another issue is the System z was designed originally to do transaction processing not the kind of workloads that are done on PCs today.

"But that said, the Z is a very powerful and fast system," Ryder says. He says the design of the and off-load engines in the mainframe such as the Integrated Facility for Linux (IFL) make it likely the system could take on some workloads not anticipated in the system's traditional design.

Users who responded to Mantissa CEO Dennis when he floated the concept last summer approached the idea with intrigue and questions.

"We can hope that the version of Windows will be more stable than Windows Vista. Moving that kind of instability into z/VM is not particularly attractive. Otherwise, on a conceptual basis, it opens up many possibilities," said a discussion participant named John Baker.

Others speculated that the technology might work better for server applications that have fewer GUI requirements that could tax the mainframe.