Ten years documents that have been unearthed by InformationWeek revealed that Microsoft attains the right to match any offer for acquisition of 30% or more of Nvidia's stock by third parties.
"Under the agreement, if an individual or corporation makes an offer to purchase shares equal to or greater than 30% of the outstanding shares of our common stock, Microsoft may have first and last rights of refusal to purchase the stock," Nvidia said in an SEC filing which was reviewed by InformationWeek.
The agreement was signed in 2001, most likely as part of the deal where Microsoft licensed Nvidia's chips for use in the Xbox 360. It is interesting to note that Nvidia lost the Xbox 360 GPU contract in 2003 to ATI, but it seems that this didn't affect Microsoft's veto power.
While Nvidia's name is synonymous in our minds with graphics cards, we must not forget that the Nvidia's ARM-based Tegra chips power a large percentage of smartphones available today, including most of Google's Android based mobiles and tablets. Over the last two years several analysts inferred that Nvidia might be a target for acquisition by Apple since its Tegra chips are ideal for the iPad; needless to say today's revelation means that Microsoft has the power to stop any deal of that kind.