The Right Way

Whether avid gaming enthusiasts or just typical users, everyone wants the best bang for their buck. And when it comes to buying processors, there are hidden opportunities in some product lines. When high-end processors are manufactured, there is always a certain percentage of those which do not meet the highest standards.

The AMD Phenom II X3

In particular, there may be problems with one or more cores, the amount of heat generated, their highest clock speed, or defects in the cache memory. If cache memory is at fault, then the faulty memory can be disabled allowing the processor to still be sold as a low-end model (e.g., Celeron & Sempron).

However, when cores are disabled at the factory because they’ve failed a test, there may not be any real-world problem with the core. This would be the case if the manufacturer needed to be more stringent in its testing methodology in order to force more processors into the budget model lines. And in most cases, these disabled cores can be unlocked and will perform without any significant issues, but currently, only AMD processors support unlocking disabled cores. In this article, we’ll give you an overview of how to do this and take advantage of value-priced processors.

First Step. Decide on a processor model which comes with one or more disabled cores. Currently, AMD ships some Phenom, Athlon, and Sempron models with single, dual, and triple cores that can be unlocked to use the additional cores. Everything depends on the processor model, so make sure you’re buying a processor with disabled cores. You should also be aware that you may not be able to unlock only one disabled core if there are others also disabled. It’s usually all or nothing, although Asus recently released new BIOS revisions which allow cores to be unlocked independently.

Second Step. Decide on a motherboard which supports AMD processors and unlocking. Though each motherboard will have its own set of options, most have an option somewhere in the BIOS (System Setup) labeled Advanced Clock Calibration (ACC). You can usually change this setting from “Disabled” to “Auto,” “Per Core,” or “All Cores.” However, use the “Per Core” option with care as some configurations can cause your system to be unstable. And with some motherboards, you may have to update the firmware (flashing the BIOS) for ACC to work properly.

Third Step. With your disabled cores now unlocked, run a stress test to ensure your system is stable. A stress test forces your processor to work at full capacity by having it process an algorithm many thousands of times.

A Quad-Core Layout

If there are any problems with your disabled cores, you will usually see errors after only a few minutes – though it is still a good idea to run the test for at least 20 minutes to ensure stability. Prime95 is an excellent utility for running stress tests, and we highly recommend it.

The Odds. The chances are very good that you’ll be successful, and the success rate is rumored to be around 70%. Accurate numbers are hard to come by because of course AMD will not provide statistics. But if you’re unsuccessful, the worst case scenario is that you bought a processor which only operates as advertised.

Also, for those of you who succeed, remember that your processor will be generating more heat from the additional cores and a stock heatsink and fan (HSF) may no longer be adequate. It’s usually a good idea to invest in a decent HSF, and ThermalTake and Zalman often have the best products in this area.

Real World. For example, we built a system with a Phenom II X2 545 processor, a Gigabyte GA-MA785GMT-UD2H motherboard, and a Kingston 2GB 240-Pin DDR3 1333Mhz stick of RAM. The Phenom processor with free shipping costs $89 on Newegg, but after unlocking the two disabled cores, it’s now the equivalent of the Phenom II X4 945 (a quad-core) which costs $166.