The X4 645 got off to an excellent start in our testing as its stock score of 11,837 in Cinebench R10 was way ahead of the Athlon II X3 455 and the Pentium G6950 at stock speeds. This result was mirrored in our WPrime testing with the X4 645 again soundly beating the other two processors at both stock and overclocked speeds. We’ll stop short of proclaiming the X4 645 the new budget CPU king however as these two heavily multithreaded programs play straight to the CPU’s strengths.
Things got more interesting when we ran the X4 645 through our Media Benchmarks, as this is comprised of both single- and multi-threaded applications. The X4 645’s stock speed score of 958 in our image editing test, for example, was well behind the 1,121 of the dual-core Pentium chip, despite it having fewer cores running at a slower speed. This really shows up the deficiencies in the ageing K10 architecture to an embarrassing degree.
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Fortunately for the X4 645, our video encoding test uses all the cores it can get, so at stock speeds the X4 645 was back on top. Things reversed when the two chips were overclocked though, with the Pentium sneaking a narrow lead of some 120 points. This pattern continued throughout our media testing proving that at stock speed the X4 645 is actually quite an attractive proposition. Unfortunately the biblically overclockable G6950 spoils the party as soon as the overclocking sauce is shared around, trouncing the X4 645 by 300 points when both are overclocked.
Gaming performance is classically less reliant on core count and more reliant on clock speeds and instructions per clock. As a result, we weren’t too surprised to see the X4 645 slip behind the G6950 in our stock speed Crysis play through, returning a minimum of only 18fps compared to the 20fps of the Intel chip. This gap widened when the two CPUs were overclocked proving that for gaming, fewer fast cores are better than more slower cores.
Power consumption figures for the X4 645 were interesting as they showed the chip to suck significantly less power than the older Rana based X3 445. This is impressive given that the X4 645 houses an extra core and indicates that some of the under the bonnet improvements AMD have made to the Propus design make it significantly more efficient. Despite this though the X4 645 drew significantly more power than the G9650 when under load at both stock and overclocked speeds.
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The X4 645 struggles to carve out a place for itself in the market. It's only averagely fast in single-threaded applications as, despite its high clock speed, it’s still based on an old architecture. For a cheap gaming rig or image editing PC we’d heartily recommend the LGA1156-based Pentium G6950 as a better buy.
The X4 645 gets a sniff of the action if multi-threaded applications are more your thing, especially at stock speeds where it thoroughly out performed the G6950. Unfortunately for AMD, the G6950 overclocks like a beast and at overclocked speeds its two cores best the four cores of the X4 645 in most applications. Add to this the fact that the Intel chip is cheaper and recommending the X4 645 becomes even harder
The only situation where the X4 645 does shine is if you already own a Socket AM2+ or AM3 system and are looking to add a little more grunt to your PC. In this case the X4 645 offers an affordable option for those looking to upgrade from a dual-core CPU, though a Phenom II X4 or X6 will serve you better if you're desperate for multi-threaded performance.