AMD Phenom II X4 940 Black Edition

Verdict: [+] DENEB Fastest and most overclockable Phenom yet [-] AGENA Still struggling to keep pace with the Q6600, let alone Core i7

To say that the original Phenom 9600 made a poor start is one of the biggest understatements of recent years. AMD spent so long developing its first quad-core desktop CPU that by the time it finally started shipping in December 2007, the CPU was massively outpaced by the ever growing range of Intel Core 2 Quads. The original Phenoms consumed huge amounts of power, suffered from a Translation Lookaside Buffer (TLB) bug and had little overclocking potential. Later models, such as the Phenom X4 9850 Black Edition, were based on the
revised B3 stepping, which fixed the TLB bug and was a little faster and more overclockable. The B3 Phenom was a step in the right direction for AMD, but it still couldn’t compete with Intel’s quad-core processors. Almost a year later, AMD is making a third attempt at Phenom with the launch of the Phenom II X4 940 Black Edition. As the insertion of the ‘II’ suggests, this new processor isn’t simply a new stepping, but a heavily redesigned chip. The two most notable improvements are a die shrink from 65nm to 45nm transistors, and 6MB of Level 3 cache instead of 2MB. SMALLER, FASTER, COOLER The shift to a 45nm manufacturing process provides several key benefits
for Phenom II. The most obvious is that AMD has been able to ramp up the clock frequency of this top-of-the-range Phenom II X4 940 Black Edition to a far more respectable 3GHz. Even better, this has been achieved while cutting power consumption. In our tests, we measured a test PC with the 2.5GHz Phenom X4 9850 Black Edition sucking as much as 236W from the wall, while the same machine with a 3GHz Phenom II X4 920 drew only 200W. This is despite both CPUs having a quoted TDP of 125W. The new Phenom II also runs a lot cooler than the old Phenom, and has improved power-saving technology in the form of Cool’n’Quiet 3.0. As with any AMD64 processor, this is better disabled when overclocking. AMD estimates that the increase in the amount of Level 3 cache provides an additional 6 per cent extra performance over an old Phenom running at the same frequency. AMD also hinted that it has made several improvements to the underlying AMD64 architecture, but hasn’t been forthcoming about the specifics. Despite repeated requests for more information, AMD would only confirm that, clock-for-clock, it expects these improvements to yield a further 4 per cent performance increase over Phenom. Unlike Intel’s Core i7 (see Issue 64, p36), which requires you to buy a new motherboard, cooler and RAM, Phenom II is pin-compatible with Phenom. This means that it should work in any Socket AM2+ motherboard that’s capable of handling a 125W processor, although a BIOS update may be required. AMD has plans for an upgraded Phenom II with a DDR3 memory controller later in 2009, but for now, the company thinks that forcing customers to buy expensive new memory for little performance benefit (Intel, take note) isn’t a good strategy. AMD is initially launching two Phenom II X4 CPUs, the 940 Black Edition and the 920. The Phenom II X4 920 has a clock speed of 2.8GHz for its £173 price, while the £203 Phenom II X4 940 Black Edition is clocked at 3GHz. As the 920 has a locked multiplier and we’ve rarely seen Socket AM2+ motherboards exceed HTT speeds of 240MHz, it looks like a poor choice for overclocking. Conversely, the 940 Black Edition has an unlocked multiplier, so it should be easy to overclock. PERFORMANCE Although the Core i7-920 and the Phenom II X4 940 are comparatively priced, the cost of an LGA1366 motherboard, cooler and memory would make a Core i7 PC cost significantly more than a Phenom II system. The Core i7 scores are shown only for those interested in comparing the latest CPUs from Intel and AMD. The serious competitor for Phenom II is the Core 2 Quad Q6600. This aging 65nm quad-core CPU first appeared at the end of 2006, yet thanks to its low price (at one point you could buy one for less than £120) and incredible overclocking potential (it can be overclocked from 2.4GHz to 3.6GHz with a £15 HSF), this CPU outsold all other quad-core CPUs. In short, the Q6600 was the nemesis of the Phenom. At stock speeds, the Phenom II 940 achieved an overall score of 1,135 in our Media Benchmarks, making it AMD’s first CPU to achieve a four-digit overall score. In comparison, the Phenom X4 9850 Black Edition scored just 897 overall in the same system. It may have taken AMD two years, but the company has also finally managed to beat the Q6600 at stock speeds, as the Intel CPU scored 1,038 overall. Phenom II also took the lead in Cinebench R10, posting a score 23 per cent higher than the Phenom and 13 per cent higher than the Q6600. The good news continued in wPrime 32M and Folding@home, in which the Phenom II was once again much faster than the Phenom and the Q6600. However, Crysis bucked this trend with the Q6600 edging head of the Phenom II, while both CPUs significantly outperformed the Phenom. OVERCLOCKING Previous Phenoms ran so hot that you’d be lucky to increase their clock frequency by more than a few hundred megahertz. However, thanks to its die shrink to 45nm, Phenom II runs much cooler and is therefore far more overclockable. While our old Phenom X4 9850 Black Edition could only be overclocked from 2.5GHz to 2.8GHz, we could overclock the Phenom II from 3GHz to 3.6GHz. This entailed increasing the CPU multiplier from 15 to 18, and boosting the vcore from 1.336V to 1.45V. This is a fairly small overvolt, but with any more voltage applied, the system wouldn’t POST. At these settings, the CPC Media Benchmarks score for the Phenom II increased from a mediocre 1,135 to a respectable 1,306. In contrast, the overclocked Phenom scored a dire 999 overall. The G0 stepping of the Q6600 that we tested has a justified reputation for being an excellent overclocker, and we pushed it up from 2.4GHz to 3.6GHz. At this frequency, its overall Media Benchmarks score rose from 1,038 to 1,478. The overclocked Q6600 also took the lead back from the Phenom II in Cinebench R10 and Folding@home, although it still lagged behind in wPrime 32M. In Crysis, the overclocked Q6600 once again reigned supreme with a faster average frame rate. However, the Q6600 consumes a lot more power than the Phenom II when overclocked. Its 65nm transistors need a lot of extra voltage to run stably at 3.6GHz, so the overall power consumption of a PC with an overclocked Q6600 is higher than a system with an overclocked Phenom II. CONCLUSION Phenom II is a huge improvement over the first two generations of Phenom processors. It provides far better performance, lower power consumption and lower operating temperatures. It isn’t quick enough to lay the spectre of the Intel Core 2 Quad Q6600 to rest. While the Phenom II X4 940 Black Edition is quicker out of the box in most applications, the Q6600 remains the chip of choice for overclockers. The fact that a Phenom II X4 940 Black Edition will set you back £203, compared to just £145 for a Q6600, makes the Intel processor far better value for money. The choice becomes even clearer when both CPUs are overclocked, as the Q6600 outpaces the Phenom II in both applications and games. Given that LGA775 and Socket AM2+ motherboards are so similarly priced and both use DDR2, the choice is obvious – despite its two-year head start, the Q6600 retains its crown.