When it launched in early January, Phenom II's sole purpose, its raison d'?tre, was to rejuvenate AMD's ability to compete against Intel with something other than price cuts. Viewed in aggregate, benchmarks of the new CPUs prove that Sunnyvale succeeded; the X4 940 and 920 are tough opponents in the mainstream quad-core market. I don't want to downplay this achievement; a strong Deneb launch was vital if AMD is to continue as a going concern.

The problem is that Sunnyvale's future competition is locked, loaded, and launched. In the past, the question of whether AMD or Intel would hold a performance advantage "next time" was fueled by speculation and odd bits of data. In this case, Intel's "next-gen" design is already on the market and has been for several months. Nehalem is no paper tiger—it's here right now, and it'll hit the 940's current price point within 2009 (barring a major roadmap change).

So can AMD scale Phenom II to match Nehalem? We wanted to find out, because the answer will tell us how the AMD vs. Intel battle will shape up in 2009. So, we took one Phenom II 940, added coolant, overclocked it to 4.2GHz, and ran the benchmarks listed below.

Cost comparison

We've known from the start that Phenom II would primarily target Core 2 Quad processors rather than Core i7. AMD definitely hit its target; Phenom II compares well against Intel's 45nm Yorkfield processors. A Phenom II X4 940 (3GHz) is currently $229 at Newegg while the Phenom II X4 920 (2.8GHz) is $195. Intel currently offers the Q9400 (2.66GHz, 6MB L2) at $229, the older 65nm Q6600 Kentsfield at 2.4GHz at $194.99, and the Q8300 (2.5GHz, 4MB L2) at $189.99. All of the Core i7 parts are significantly more expensive than the Phenom II X4 940; the Core i7 920 is $294.99 while the 940 is $565.

So how much bang does Phenom give for the buck?

Performance Summary

Worldbench 6b2: Phenom II is more than adequate for any office or content creation work, but can't match Intel's Core i7-965 even when overclocked. Typically, however, these types of workloads don't require anything like ultra-powerful hardware.

Phenom II is more than adequate for any office or content creation work, but can't match Intel's Core i7-965 even when overclocked. Typically, however, these types of workloads don't require anything like ultra-powerful hardware. Photoshop CS4: Intel's Core i7-965 led our Photoshop benchmark with the overclocked Phenom II not far behind. The standard Phenom II trailed the pack, but again, all of the processors turned in good performance numbers.

Intel's Core i7-965 led our Photoshop benchmark with the overclocked Phenom II not far behind. The standard Phenom II trailed the pack, but again, all of the processors turned in good performance numbers. Handbrake 0.9.3: This x264 encoder scales well across all eight of Core i7's logical processors; Phenom II at 4.2GHz can't match the slower Core i7-920.

This x264 encoder scales well across all eight of Core i7's logical processors; Phenom II at 4.2GHz can't match the slower Core i7-920. Cinebench R10: Phenom II X4 940 is the slowest of the four cores we tested (though not by much), while the 4.2GHz flavor smashes everyone else in single-thread testing. Core i7-965 still wins the multi-threaded test, but our overclocked AMD chip makes Intel work for it.

Phenom II X4 940 is the slowest of the four cores we tested (though not by much), while the 4.2GHz flavor smashes everyone else in single-thread testing. Core i7-965 still wins the multi-threaded test, but our overclocked AMD chip makes Intel work for it. Valve Particle, Map Compilation Tests: Another set of overall wins for Intel; Phenom II 4.2GHz can't quite match the Core i7-920. Phenom II X4 940 at stock speeds is at the back of the pack.

Another set of overall wins for Intel; Phenom II 4.2GHz can't quite match the Core i7-920. Phenom II X4 940 at stock speeds is at the back of the pack. Crysis: Phenom II is an excellent gaming chip. The X4 940 beats the Core i7-920 here while the 4.2GHz chip is only a hair back from the Core i7-965.

Phenom II is an excellent gaming chip. The X4 940 beats the Core i7-920 here while the 4.2GHz chip is only a hair back from the Core i7-965. Call of Duty 4: This is one game that's quite fond of Phenom II; the Phenom II X4 940 at 4.2GHz wins the benchmark with the stock-clocked flavor in a tie for second.

This is one game that's quite fond of Phenom II; the Phenom II X4 940 at 4.2GHz wins the benchmark with the stock-clocked flavor in a tie for second. Unreal Tournament 3: In UT3, our overclocked chip leads the rest; the standard X4 940 still outperforms Intel's Core i7-920.

In UT3, our overclocked chip leads the rest; the standard X4 940 still outperforms Intel's Core i7-920. Assassin's Creed: Another game, another good showing from AMD. Our overclocked Phenom II outperforms the Core i7-965 while the Phenom II X4 940 is again well ahead of the Core i7-920.

AMD's Phenom II X4 940 doesn't lead a majority of our tests at stock speeds, but both the Core i7-920 and the Core 2 Quad Q9650 are significantly more expensive than the AMD part. The Core i7-920 is a bit better in that regard, but LGA1366 motherboards and DDR3 still command a price premium over AM2+ and DDR2.

AMD's new chip competes well against the Intel parts it's priced against, has plenty of overclocking headroom even if you don't have a phase-changer handy, and offers excellent gaming performance. Compared to the Phenom that proceeded it, Phenom II is a slam dunk. Whether or not that's enough to save AMD, particularly in the current economic climate, is regrettably an open question.

Test Setup, SiSoft Sandra

Components Nehalem Deneb Processor Core i7-965/920 Phenom II X4 940 Clockspeed 3.2GHz/2.67GHz 3.0GHz/4.2GHz Motherboard Intel DX58SO "Smackover" Asus M3A79-T Deluxe Operating System Vista Ult. 64-bit w/SP1 Vista Ult. 64-bit w/SP1 Video Card ATI Radeon HD 4870 ATI Radeon HD 4870 Storage 80GB Intel SSD 80GB Intel SSD Power Supply PC Power & Cooling 750W PC Power & Cooling 750W

Results for the QX9650 are only intermittently available; configuration details on that system are available here. Other reviews at other places have done a thorough job comparing Phenom II's performance against that of Intel's Core 2 Quad series; we've focused our review in a different direction.

On that note: I've labeled the QX9650 as a "Core 2 Quad QX9650" in the review. Technically, the part we tested is an Intel Core 2 Extreme QX9650, but that $1,000 part has been replaced by a Core 2 Quad Q9650 selling at a third the price of the original.

Both test systems were configured for dual-channel / triple-channel operation; the same brand of DDR2 and DDR3 was used in all cases. The Phenom system used 4GB of DDR2-1066 RAM in a 2GB/2GB configuration while the Core i7 processors used 4GB of DDR3-1066 in a 2GB-1GB-1GB deployment.

Configuring the Core i7 in this manner could result in a performance loss but only one test—Sandra's theoretical memory bandwidth benchmark—gave results that might be interpreted as evidence of such. All of the Core i7-965 benchmarks were run again on the system; a comparison between the performance of the processor in this review vs. the performance we saw in our Nehalem launch coverage shows little-to-no difference.

The Asus M3A79-T will not run in dual-channel mode if three DIMMs are inserted. I'm not sure if this is a characteristic of the 790GX chipset or an errata that's unique to the Asus board, but it makes it impossible to perfectly synchronize the DIMM loadouts between the two processors while keeping both in triple channel/dual channel mode. Given this fact, 2GB-1GB-1GB for Core i7 was deemed the best option.

As for why we didn't compare an overclocked Nehalem against an overclocked Deneb, the answer is fairly straightforward: the point of our investigation is to look at how Phenom II scales, and not at how Nehalem scales.

The cooler head on the phase change unit I used hovered between -50C and -60C; actual CPU temp as reported in the BIOS was -40C. The accuracy of BIOS temperature readings at these temperatures is questionable, but that's what the ASUS board consistently reported.

I also tested the Gigabyte GA-MA790GP-UD4H, but ultimately opted for the ASUS board. Stability between the two was equal, but the ASUS model proved more overclocking-friendly—I was able to reach 4.2GHz on the M3A79-T vs. just 4GHz stable on the Gigabyte system.

HyperThreading was kept on for all of the Core i7-965 and Core i7-920 benchmarks.

Note: defining the phrase "stable overclock"

For a word that's defined as able or likely to continue or last; firmly established; enduring or permanent, "stable" becomes exceptionally slippery when combined with "overclock." To some in the overclocking community, a stable overclock is achieved when one is able to boot into Windows, run SuperPi (a single-threaded benchmark that's long-since outlived whatever dubious worth it once possessed), and take a few CPUID screenshots. This is far below what I personally find acceptable.

I consider an overclock to be stable if and only if the system is capable of executing a review-level/comprehensive suite of benchmarks without crashing, rebooting, or exhibiting any behavior that is not also displayed when the system is running at stock speeds. If a CPU can loop 3DMark Vantage's CPU tests or continuously re-render an animation for an indefinite period of time at stock speeds but crashes after 30 minutes when asked to do so in an overclocked state, the overclock is unstable. This is still the case even if the system has completed multiple iterations of the benchmark in question.

It's not easy to fine-tune a system to such a standard while simultaneously attempting to push a processor as far as it can go; it took me several weeks to find the precise edge between stable/unstable for the Phenom II X4 940 that's the subject of this review. Meanwhile, the Phenom X4 9950 that we also tested presented its own unique challenges when combined with a phase-change cooler—I'll provide additional detail on my overclocking adventures later in the review. In the end, I was able to completely stabilize our Phenom II X4 940 at 4.2GHz even with an HT link speed of 210MHz (1.89GHz effective), an IMC/L3 clock of 2.53GHz (up from 1.8GHz base) and an 1170MHz memory clock. Setting the HT link multiplier to 1x and keeping the IMC/L3 clocked at 1.8GHz increased my maximum stable clockspeed, but I thought the tradeoff a poor one. More details to follow.