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AMD Phenom II X4 965 = $185
The cream of the crop of AMD processors today is the Phenom II X4 965 Black Edition, a high performance quad-core part with a modest price tag. Amazingly, this 3.4GHz quad-core that features a 6MB L3 cache and works on all current AMD motherboards (AM2/AM2+/AM3) is priced at just $185.
The Phenom II X4 965 with its unlocked multiplier is a flexible processor that should cater well to all type of users, for both upgrades and new systems built from scratch.
Given that the processor works on motherboards that are over 3 years old, it works as an ideal upgrade path for those using older AM2/AM2+ based platforms. Those looking to build a brand new system should also consider coupling the Phenom II X4 965 with the latest AM3 platform that was just updated with a brand new chipset.
AMD Phenom II X4 925 = $140
The Phenom II X4 is the only series in our round-up to feature two different models. Along with the powerful X4 965 at the top of the food chain, towards the bottom we have the Phenom II X4 925 selling for $140. In our opinion the Phenom II X4 925 is not quite as good value as the more expensive 965 version, as it loses 600MHz and the unlocked clock multiplier.
The 18% reduction in clock speed comes at a 24% price cutback. That said, the Phenom II X4 925 is a worthy overclocker in its own right, and at $140 is one of the cheapest quad-core processors featured in this article.
AMD Phenom II X3 720 = $140
The Phenom II X3 720 Black Edition was introduced about a year after AMD released the world's first triple-core processors. At just over $100 this is the premium model, operating at 2.8GHz with the 6MB L3 cache. Designed for the AM3 socket with DDR3 memory support, this processor is nonetheless also backwards compatible with the AM2/AM2+ platforms.
Almost all Phenom II X3 processors have a serious trick up their sleeves and that is the ability to transform into a fully fledged quad-core processor. When paired with the right motherboard with a SB710 or SB750 south bridge and a BIOS that offers Advanced Clock Calibration (ACC), it is possible to enable the fourth core of many Phenom II X3 processors.
It should be noted that AMD disabled the ability to enable cores with their 890GX chipset, as the SB850 south bridge removes ACC support. However, motherboard manufacturer Asus has already announced that their 890GX products feature a workaround and can still enable extra cores. Although we are working off retail pricing for this article, OEM versions of this processor can be had for a little over $100.
AMD Athlon II X4 635 = $120
Those looking for a cheap quad-core will love what the AMD Athlon II X4 has to offer. This 2.9GHz quad-core processor supports the latest AM3 socket and the past AM2/AM2+ platforms, costs just $120 and represents the flagship model of the series.
The Athlon II processors differ from the more expensive Phenom IIs primarily on the absence of a L3 cache. While the L2 cache is still just 512KB per core, the L3 cache has been disabled (versus 6MB on the Phenom II). This results in a considerable impact on performance, though at $120 the Athlon II X4 635 still represents an exceptional level of value.
AMD Phenom II X2 555 = $100
We barely accomplished to include a dual-core AMD processor in this comparison. Their most expensive model, the Phenom II X2 555 Black Edition costs just $100. This 3.2GHz dual-core processor receives the full 6MB L3 cache and is again essentially a Phenom II X4 with two cores disabled.
As with the triple-core CPU above, with the right motherboard and BIOS configuration it is likely that the other two cores can be enabled, turning the $100 Phenom II X2 555 into a Phenom II X4 955 Black Edition by changing a single BIOS setting.
For the average computer user the Phenom II X4 955 still provides a serious level of performance, generally scoring higher than almost all the Intel Core 2 Duo processors, or about on par with the Intel Core 2 Duo E8500, which is considerably more expensive at $190. The Phenom II X4 955 can also be used with all AM3 and AM2/AM2+ motherboards.