AMD Slapped With Class Action Lawsuit Over Deceptive Core Count In Bulldozer CPUs

When Advanced Micro Devices (AMD) introduced its Bulldozer architecture, it talked about the design being a "third-way" approach between symmetric multithreading (SMT), like Intel's Hyper Threading, and true multi-core processing where multiple discrete cores reside on a single die. Now AMD will have to defend its design and the way it was marketed because of a class-action lawsuit.

The lawsuit, filed by Tom Dickey in the U.S. District Court for the Northern District of California, San Jose Division, alleges that AMD deceived customers by overstating the number of cores on its Bulldozer processors. With regards to Bulldozer-based processors sold and marketed as 8-core chips, Dickey and the lawsuit claim that the true number of cores is only half that.

AMD FX-8150

These are murky waters the lawsuit is wading in. It's effectively asking a court to define what constitutes a core, and seemingly do it in simple terms. However, processors are complex things -- it's not easy to come up with a one-size-fits-all definition and wrap a bow on it.

The definition the lawsuit shoots for is the ability of a core to perform instructions simultaneously and independently of other cores, which it claims Bulldozer does not. This is where AMD's so-called third-way design comes into play. Let's have a look.

AMD Bulldozer Architecture

Bulldozer plops multiple discrete x86 cores on one die. To do that, AMD starts with two discrete cores (above left), eliminates some duplicate logic, and then fuses the pared down cores into a single, shared design (above right).

AMD Bulldozer Die Map

The above die map shows the design of an 8-core Bulldozer processor. Each of those modules contains two cores, but share a single floating point unit (FPU), as well as fetch and decode resources. According to the lawsuit, it's wrong of AMD to market such a design as an 8-core chip. It further alleges that the typical consumer doesn't have the tech savvy to understand the inner workings of a computer chip, and that AMD misled them.

Dickey's class-action lawsuit seeks unspecified damages, litigation expenses, pre- and post-judgement interest, and other injunctive and declaratory relief  as is deemed reasonable.