Judge Allows Lawsuit Over AMD's FX Processors to Continue


U.S. district judge Haywood Gilliam has allowed the class-action lawsuit alleging that AMD misled its customers about the number of cores in its FX CPUs to continue. According to the lawsuit, which was filed in 2015, the shared cores utilized by the FX processor line's Bulldozer modules shouldn't have been counted individually.

We explored the Bulldozer concept when we reviewed the FX-8150 back in 2011. AMD had previously taken a bit of a holier-than-thou approach to counting cores because it believed Intel's Hyper-Threading, which offers two logic processors for each physical core, was disingenuous. But then AMD developed the Bulldozer module to share "instruction fetch and decode stages, floating-point units, and the L2 cache" between two cores and changed its tune.

This is where the lawsuit comes in. Some people who bought the FX-8120, FX-8150, FX-8320, FX8350, FX-8370, FX-9370, and FX-9590 processors believe AMD misled them with its claims about how many cores the processors had. The company marketed its FX processors as the world's first eight-core CPUs, but because of the shared resources between cores in Bulldozer modules, the lawsuit alleges that this claim was deceptive about real-world performance.

We pointed out nearly a decade ago that AMD had suddenly changed its definition of what a "core" is for these processors:

"To best accommodate its Bulldozer module, the company is saying that anything with its own integer execution pipelines qualifies as a core (no surprise there, right?), if only because most processor workloads emphasize integer math. I don’t personally have any problem with that definition, but if sharing resources negatively impacts per-cycle performance, then AMD necessarily has to lean on higher clocks or a greater emphasis on threading to compensate."


AMD's goal for Bulldozer modules was to offer many of the benefits of having a bunch of cores without actually having to, you know, use completely separate cores. The company said at the time that a Bulldozer module could average 80% the performance of two complete cores. But the lawsuit's plaintiffs weren't looking for eight-core processors that performed like six-core processors; they wanted the performance of eight individual cores.

Gilliam decided in January 2019 to reject AMD's request to dismiss the lawsuit because several of the plaintiffs (allegedly) knew exactly how its Bulldozer module worked prior to purchasing the processors. This isn't an outright victory for the plaintiffs--Gilliam is merely allowing the lawsuit to proceed--but it does mean AMD can't just steamroll the lawsuit out of the court. Everyone heads back to court on February 5 to discuss the case.