A class action lawsuit has been filed against chip-maker AMD for allegedly tricking consumers into buying its Bulldozer processors by overstating the number of cores contained in the chips. The suit claims that while Bulldozer was advertised as having eight cores, functionally it actually only had four.

AMD's multi-core Bulldozer chips use a unique design that combines the functions of what would normally be two discrete cores into a single package, which the company calls a module. Each module is identified as two separate cores in Windows, but the cores share a single floating point unit and instruction and execution resources. This is different from Intel's cores, which feature independent FPUs.

The suit claims that Bulldozer's design means its cores cannot work independently, and as a result, cannot perform eight instructions simultaneously and independently. This, the claim continues, results in performance degradation, and average consumers in the market for a CPU lack the technical expertise to understand the design of AMD's processors and trust the company to give accurate specifications regarding its CPUs.

Because AMD did not convey accurate specifications, the suit argues that tens of thousands of consumers were misled into buying a Bulldozer CPU that cannot perform in the same way as a true 8-core CPU. Allegedly, this would mean AMD violated the Consumer Legal Remedies Act, California’s Unfair Competition Law, and was guilty of false advertising, fraud, breach of express warranty, negligent misrepresentation, and unjust enrichment.

AMD is being sued for damages, including statutory and punitive damages, litigation expenses, pre- and post-judgment interest, as well as other injunctive and declaratory relief as is deemed reasonable.