Owners of Apple, Dell and Hewlett-Packard laptops have combined their lawsuits against Nvidia in an attempt to force the graphics chip maker to replace allegedly flawed processors, according to court documents.

If granted class-action status, the case could involve millions of laptop computer owners, the plaintiffs said.

The five plaintiffs, including a Louisiana man who bought an Apple MacBook Pro a year ago, filed an amended complaint last week in a San Francisco federal court, accusing Nvidia of violating consumer-protection laws.

Nvidia admitted to the problem in July 2008, when it said some older chipsets that had shipped in "significant quantities" of notebooks were flawed. In a subsequent filing with the U.S. Securities and Exchange Commission (SEC), the company argued that its chip suppliers, the laptop makers and even consumers were to blame.

Nvidia later told the SEC that it would take a $196 million charge to pay for replacing the graphics processors.

Apple, Dell and HP have all told users that some of their laptops contain faulty Nvidia chipsets. Apple, in fact, essentially said that Nvidia had misled it. "Nvidia assured Apple that Mac computers with these graphics processors were not affected," Apple said in a support document posted last October. "However, after an Apple-led investigation, Apple has determined that some MacBook Pro computers ... may be affected."

Although Apple promised it would repair any defective MacBook Pro for two years after its purchase date, whether it was in warranty or not, HP and Dell first issued BIOS updates designed by Nvidia that boosted fan speed. The increased fan speed was intended to ward off chip failure. Later, however, both companies also extended warranties for the affected laptops, and in some cases offered free repairs.

The plaintiffs in the combined lawsuit said that anything other than a replacement of the flawed chips was insufficient. "This is a grossly inadequate 'remedy,' as it results in additional manifest defects, including, without limitation, further degraded battery life, system performance and increased noise in the Class Computers," the complaint read.

"Worse, this 'remedy' fails to solve the actual problem. Instead, this measure only ensures that the Class Computers will fail after the OEM's express warranty period expires, potentially leaving consumers with a defective computer and no immediate recourse," the lawsuit continued. "Finally, even after this purported 'update,' video and system performance is still degraded due to unacceptably high heat and part failures."

Todd Feinstein of Louisiana was the one plaintiff who had purchased an Apple laptop. After buying a MacBook Pro in April 2008, the computer ran hot, periodically shut down without warning and displayed only gray or black at times, Feinstein said.