Are Phenom X3s Defective Quad Core Processors?
There has been a great deal of speculation around the Internet surrounding the origin of the Phenom X3 processors. The most common statement I hear is that “Triple core processors are defective quad cores—shut off the faulty core and you’ve got a working triple core”. I decided to speak to AMD regarding this to get their official stance. I had a good conversation with our contact at AMD on the subject.
To put it simply, AMD’s K10 design is very flexible in that certain parts of the die can be fused off to produce other product lines—like the X3 and even dual-core parts. All of AMD’s Phenom dies are produced alike and they are later screened and selected for AMD’s various products. One test that is conducted is maximum attainable frequency at a set voltage. Each core is tested individually—not just the chip as a whole. A chip able to clock comfortably on all cores to 2.4GHz would likely become a Phenom X4 9750, for example.
There could be a situation, however, where the first three cores are able to clock to 2.4GHz comfortably but the fourth could only manage about 2.1GHz. Rather than downgrade the entire chip to the frequency of the weakest core—2.1GHz, AMD can disable this core to produce a 2.4GHz triple core. In a situation where there are two weaker cores, AMD can produce dual-core Phenom processors.
So this 2.4GHz triple core has three fully functional, fully qualified cores, and all of the other shared processor components, including the full 2MB L3 cache. It is not really accurate to say that one of the four cores is “broken”. It likely just didn’t have the same clock speed potential as the other three.
It should also be noted that this fourth core is completely disabled—it is not simply hidden from the BIOS or operating system. It is electrically shut-down so as not to consume unnecessary electricity.
Being able to use Phenom dies that may have one weak core certainly makes very good business sense. Rather than tossing the chips or producing slow quad core processors, higher speed, fully functional X3s can be produced. I think AMD’s approach is very logical.
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