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When is a CPU core not a CPU core? It's now up to a jury of 12 to decide.

posted by takyon on Wednesday January 23 2019, @09:22PM   Printer-friendly
from the class-excavation dept.

An Anonymous Coward writes:

Core blimey... When is an AMD CPU core not a CPU core? It's now up to a jury of 12 to decide

A class-action lawsuit against AMD claiming false advertising over its "eight core" FX processors has been given the go-ahead by a California judge.

US district judge Haywood Gilliam last week rejected [PDF] AMD's claim that "a significant majority" of people understood the term "core" the same way it did as "not persuasive."

What tech buyers imagine represents a core when it comes to processors would be a significant part of such a lawsuit, the judge noted, and so AMD's arguments were "premature."

The so-called "eight core" chips contain four Bulldozer modules, the lawsuit notes, and these "sub-processors" each contain a pair of instruction-executing CPU cores. So, four modules times two CPU cores equals, in AMD's mind, eight CPU cores.

And here's the sticking point: these two CPU cores, within a single Bulldozer module, share caches, frontend circuitry, and a single floating point unit (FPU). These shared resources cause bottlenecks that can slow the processor, it is claimed.

The plaintiffs, who sued back in 2015, argue that they bought a chip they thought would have eight independent processor cores – the advertising said it was the "first native 8-core desktop processor" – and paid a premium for that.

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  • (Score: 2) by zocalo on Wednesday January 23 2019, @09:57PM

    by zocalo (302) on Wednesday January 23 2019, @09:57PM (#790836)
    That was my take at the time too, although I actually went with Intel for reasons related to available motherboard options. To me "core" implies the actual microprocessor element that executes instructions, not the cache and all the other stuff that goes into a CPU "package", which in turn are now often assembled from multiple sections of silicon within the chip. The whole debate over hyperthreading and per-core licensing essentially comes down to this as well; it creates two virtual execution cores from one - it doesn't virtualise the cache or anything else, yet shows up in resource monitors as two CPUs.

    The chip layout block diagrams were public, as were the various benchmarks and reviews, and there's always going to be shared elements, at some point - especially on the IO side of things. I don't think it's AMD's fault if they didn't do their homework, especially if they got bitten by the shared FPU for an FPU heavy workload, or the shared cache for a CPU heavy one. Besides, by that point the number of cores, clock speed, cache sizes, etc. were all just a soup of mostly meaningless numbers anyway. If you weren't buying based on the bang per buck of performance benchmarks for the kinds of tasks you were buying a given chip for, and ideally doing those tests yourself using actual real-world dataset, then you were doing it wrong.
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