Phenom X4 processors could hardly be considered an overclocker choice. They could rarely be overclocked past 3.2GHz frequency using air-cooling. Therefore, overclocking fans preferred quad-core Core 2 Quad CPUs that could reach much higher speeds with less effort in most cases.
Phenom II X4 seems to be much more interesting in this respect. These processors are made with new 45nm process that improved their frequency potential dramatically and theoretically can push back the overclocking limits, too.
To see if this is in fact the case, we tried overclocking Phenom II X4 940 processor sample available in our lab. This CPU belongs to the Black Edition series, so it features an unlocked clock frequency multiplier. As a result, it is much easier to check out its maximum frequency potential. Having increased the core voltage from the nominal 1.35V to 1.55V and using a Scythe Mugen air cooler we got our CPU running stably at 3.8GHz by simply raising the clock frequency multiplier.
So, new Phenom II X4 processors do have very good frequency potential: the top model overclocked by 26% with air cooling only. So, the new AMD processor seems to be quite fit for overclocking experiments. However, we would like to make sure that potential Phenom II X4 owners keep in mind: 3.8GHz frequency will not let a CPU on Stars (K10) microarchitecture work as fast as overclocked Core 2 Quad from the same price range could.
For example, Core 2 Quad Q9400 processors priced close to Phenom II X4 940 can be easily overclocked to the same 3.8GHz. However, our tests showed that Phenom II X4 CPUs working at 3.0GHz nominal speed are averagely slower than Core 2 Quad Q9400 at the nominal 2.66GHz. As a result, if we increase the processors frequency to the same level, Phenom II X4 will still be noticeably slower.
It means that Phenom II X4 may actually appeal to overclockers only as an alternative to less overclockable Intel CPUs. Among them there is the disappearing Core 2 Quad Q6600 on a 65nm Kentsfield core or 45nm quad-core processors with low multipliers, such as Core 2 Quad Q8200 or Q8300. However, it doesn’t make sense to compare their performance during overclocking against that of an overclocked Phenom II X4 940, because AMD’s solution is in fact more expensive.
Therefore, we assume that a less expensive Phenom II X4 920 may actually be more appealing to overclockers. However, we do not have a CPU like that at this time, so we cannot check out its potential yet.