NVIDIA has a special deal with Microsoft to prevent outside deals and possibly let Microsoft itself buy it out, according to SEC filings. The Windows developer has rights of refusal on any attempt by a company to buy more than 30 percent of NVIDIA's share, preventing any other company from buying a controlling stake. NVIDIA also has "poison pills" that would let it issue shares without shareholder approval to prevent a controlling stake, and its shareholder voting rules would prevent an activist investor from easily overthrowing management.
