Microsoft said on Thursday that it has begun public trials of new virtualization software that competes with programs from VMware, saying the tests are starting ahead of schedule.
VMware shares fell 6 percent and Microsoft shares rose 2.5 percent following Microsoft's announcement that it has released the trial software, known as Hyper-V.
Microsoft said it previously told customers the first public release of the test version of Hyper-V would come out in the first quarter of next year.
Global Equities Research analyst Trip Chowdhry said the release of the trial versions of the Microsoft virtualization programs, which comes on the heels of Oracle's unexpected entry last month into the market for virtualization software, is bad news for VMware.
Mr. Chowdhry said engineers at Microsoft have told that him Microsoft's virtualization programs are three times as efficient as those from VMware. Oracle has publicly made a similar claim.
EMC, which owns a majority stake in VMware, fell 3.7 percent.
VMware representatives could not immediately be reached for comment.