AMD's Phenom II 940 guns for the Core 2 Quad Q9400

Product: AMD Phenom II 940
Price: $275 (USA), £230 approx (UK)

PHENOM MARK ONE was the proverbial wet fart, really. When the 9700 arrived, as part of the Spider platform, it drew a lot of power and couldn’t even keep pace with Intel’s cheapest Core 2 Quad Q6600.

But we’re in the 45nm era now, so step forth AMD’s new flagship CPU, the 3GHz Phenom II 940. In a nutshell, the new Phenom II 940 and the slower 2.8GHz Phenom II 920 (not tested here) are Deneb cores built with 45nm SOI tech. Each has four cores, a 125W TDP, a 1.8GHz (3.6GHz full duplex) Hypertransport bus and 4MB more L3 cache than previous Phenoms, giving a total 8MB cache.

 

The 940 and 920 are AM2+ package processors that support AM2+ motherboards as long as the Bios has been updated to support the latest CPUs. AM3 motherboards and AM3 Phenom IIs with DDR3 memory support will arrive in the second quarter of 2009. AM3 Phenoms will work with AM2+ motherboards (without DDR3 Ram support) but AM2+ Phenoms won’t work in AM3 motherboards.

AMD says Phenom II 940 is part of its Dragon platform, which consists of a Phenom II processor, a 790GX motherboard and an ATI Radeon HD 4800 series graphics card. Call us cynical old geeks, but the Dragon platform, like the Spider platform before it, is nothing more than a marketing programme. AMD’s own guidelines say a Dragon system with Phenom II 940 at 3GHz with 4GB Ram, a Radeon 4870 and WD Raptor hard drive should draw around 150W when idling. In fact, our system drew considerably less, which we’re happy to attribute to a Geforce GTX 260 card, so that’s one instance where the Dragon set of components isn’t necessarily the best.

 

AMD claims the Phenom II offers a 20 per cent performance increase compared with the Phenom 9950. More instructions per clock, a higher frequency and 4MB more cache are the heroes of the day. It’s interesting to note that AMD’s slide show only shows a limited four(ish) per cent performance increase due to DDR3, so the much cheaper DDR2 Ram should provide the best bang for buck for the foreseeable future.

AMD asked us to compare the Phenom II 940 to a Core 2 Quad Q9400, one of Intel’s cheapest Penryn quad cores that AMD says the Phenom II 940 will match closely in terms of price. As well as comparing the Phenom II 940 to the Core 2 Quad Q9400, we’ve chucked in the Core 2 Extreme QX9650 (which has the same 3GHz frequency as the Phenom II 940), a top of the range Core i7 965 and an old-school Phenom 9950 Black Box edition.

Phenom II 940 (left) and Core 2 Quad Q9400 (right).

Benchmark setup

Windows Vista Ultimate 64bit Service Pack 1

MSI DKA790GX (790GX) Platinum motherboard (Phenom)

Gigabyte GA-MA790GP-DS4H (790GX) motherboard (Phenom, 3DMark Vantage test only)

Intel DX58SO (X58) motherboard (Core i7)

ECS P45T-A (P45) Motherboard (Core 2 Quad)

Corsair 2GB 1,066MHz DDR2 CM2X1024-8500C5D with 5-5-5-15 timings (Phenom, Core 2 Quad)

Kingston HyperX 3GB 2,000MHz DDR3 KHX1600D3T1K3/3GX @ 1.6Ghz with 9-9-9-24 timings (Core i7)

Nvidia Geforce GTX 260 192-shaders 896MB DDR3 (180.48 drivers)

Western Digital Raptor 150GB

Asus BC-1205PT Blu-ray drive

Enermax Infiniti 720 power supply

Akasa AK-876 cooler (Phenom)

Akasa AK-965BL cooler (Core 2 Quad)

Akasa Nero cooler (Core i7)

 

System notes

Intel’s X58 motherboard enables turbo boost for the Core i7 by default and it therefore seemed unfair to disable this. As a result, we tested with the CPU running at 3.46GHz (26x133MHz) rather than the 3.2GHz (24x133MHz) it is usually advertised as operating at.

All the Phenom scores are taken with an MSI 790GX motherboard, with the exception of 3DMark Vantage, where the MSI board produced some unexpected results with the overclocked Phenom. We’ve therefore stated the 3DMark Vantage results from a Gigabyte 790GX motherboard (in a last minute dash we also re-did other benchmarks on the Gigabyte board just to confirm other benchmarks produced the correct result with the MSI board. And yes, scores remained within +/- 3 per cent).

Overclocking

AMD provided us with overclocking guidelines that stated: "On normal air cooling you will probably see results between 3.65GHz...3.90GHz”. We were able to boot into Windows at 3.9GHz (using multiplier only), but it was unstable at such a high frequency. For a completely stable system, we couldn’t push our CPU ratio beyond 18.5 (resulting in 3.7GHz clock) with a core voltage of 1.55. Increasing the voltage to 1.60 and 1.65, as AMD’s overclocking notes suggest for systems with advanced cooling, didn’t let us move the ratio up any further.

Increasing the CPU reference bus frequency, even by tiny amounts, resulted in instability. So we stayed at 3.7GHz for rock-solid reliability when benchmarking. AMD says “a 32-bit OS will likely allow slightly higher overclock results (in general) compared to a 64-bit OS” so our choice of 64-bit Vista may have held us back a little. There’s no doubt that many punters will get 3.9GHz out of their Phenom II 940s with the right CPU (since every one reacts differently to overclocking), a really big air cooler and a better motherboard.

On that note, since the reference bus and Ram frequencies are linked due to the CPU-integrated memory controller, our Ram frequency went up as our the bus speed went up. These small increases may have been what tipped our system over, since the MSI 790GX motherboard really hated custom memory timings and voltages – we went through four different premium brands of Ram before getting a set that worked reliably with the MSI board.

Our Phenom II 940 idled at 36˚C at 3GHz and 47˚C when overclocked, which isn’t a bad result at all.

Benchmark graphs and observations

PCMark05 does a lot of real world tests including XP start-up time, web page rendering, video encoding, etc. In the overall test, which stresses every component in the PC, AMD's Phenom II 940 does a great job, keeping pace with Intel's expensive QX9650. In the CPU specific test, which focuses on tasks like file compression, encryption and audio encoding, the Phenom II is the outright winner with the Core 2 Quad Q9400. Overclock it and it speeds past even the 3.46GHz Core i7, which is very impressive. Things get a little hairy for the Phenom II in the memory suite as it clearly loses to the Core 2 Quad Q9400, but it has been claimed that the memory benchmark is optimised better for Intel chips.

PCMark Vantage is a jack of all trades benchmark. It shows how AMD’s latest chipset and CPU does an excellent job against Core 2 Quad PCs but AMD is significantly behind Intel’s Core i7 architecture.

In Cinebench 10, a 3D CPU rendering test, the Phenom II 940 competes directly with mid-range Penryn Core 2 Quads. The Core i7’s hyperthreading gives it a sizable advantage over other processors and gives it a super efficient speed-up factor.

The Dhrystone test is the classic measure of CPU performance, while the Whetstone test measures floating-point operation speed where a higher score benefits scientific and CAD programs. The Core i7 runs the Whetstone test with SSE4.2 extensions enabled, giving it a distinct advantage. As programs are optimised for Core i7 architecture, this kind of performance gap between Core i7s and other processors may become visible.

Core i7’s integrated triple channel memory controller really does deliver outstanding bandwidth. Core 2 architecture stays in the dark ages with AMD wedged in-between.

The CPU is usually the bottleneck when playing games at low resolutions. The Phenom II 940 does a poor job against Intel’s Core 2 Quad Q9400.

The graphics card is usually the bottleneck when playing games at high resolutions. It’s pointless playing Crysis Warhead with a top of the range processor if you’ve only got a mid-range graphics card. Overclocking the Phenom II 940 doesn’t let it catch a 3GHz Intel quad core in our gaming tests.

At 1,280x1,024 with performance settings enabled, 3DMark Vantage is clearly GPU-bound. Intel’s chips are all being restrained at a slightly higher boundary than AMD’s chips. We had to change to a Gigabyte 790GX motherboard for our Phenom II 940 tests in this benchmark, because at this point the MSI motherboard produced the same score for the overclocked Phenom II and the regular 3GHz Phenom II. We repeated the test several times on the MSI board (we suspect some sort of negative voltage scaling – AMD wouldn’t comment on the bizarre behaviour) but overclocking didn’t help. AMD’s poor scoring here really sums up that the Phenom II 940 isn’t a match for Core 2 Quad in the gaming arena.

Phenom IIs support Cool n’ Quiet 3.0, which cuts peak power consumption up to 50 per cent compared with Cool n’ Quiet 2.0 (featured on the Phenom 9950), according to AMD. In the real world, Cool n’ Quiet 3.0 simply downclocks the Phenom II to 800MHz when idling (with balanced power settings enabled in Vista) compared with a downclock of 1300MHz on the Phenom 9950. Despite its integrated graphics (which AMD says draw nothing when a separate graphics card is added) the 790GX chipset is also noticeably more efficient than the original “Spider” 790FX chipset, drawing up to 10 Watts less in our estimations.

The swanky Core i7 architecture doesn’t draw more or less when idling in balanced or performance power modes – that’s despite the frequency halving in balanced mode. Our Core i7 rig will have drawn more power due to the third gigabyte of Ram present.

The Phenom II 940 draws more power than the Core 2 Quad Q9400, especially if you forget to turn balanced power settings on in Vista. The gap became even more pronounced when we enabled MSI’s “green power” (which isn’t a default setting) on our Core 2 Quad test rig. Then the Core 2 Quad Q9400 system drew just 89W when idling.

Based on an eight-hour day with seven hours idling and one hour going flat out, the Phenom II 940 is £2.21 more expensive than a Core 2 Quad Q9400 per year to run in energy bills (based on an 11p/kWh tariff), so the power consumption difference isn’t that important for work PCs.

The idle power consumption of an overclocked Phenom II 940 is commendable, so long as you remember to enable balanced power settings in Vista. Power consumption sky rockets when an overclocked Phenom II 940 is put under strain, so it doesn’t make much sense for gaming rigs to use overclocked Phenom IIs when you get such a small increase in gaming performance.

We didn’t have the time (or the will) to test every processor available, but we did do some last minute tests with a Core i7 920 and Core 2 Quad Q9450. Intel’s cheapest Nehalem, the 2.66GHz Core i7 920, scored 9337 in PCMark05’s CPU test, an area where the Phenom II 940 excelled. That’s three per cent quicker than the Phenom II 940 and confirms pretty emphatically that the Phenom II is not a threat to the Core i7 line-up. The Core 2 Quad Q9450 has twice the L2 cache of the Q9400 and is only a tiny bit more expensive. The only benchmark the Q9450 did better in was the Cinebench mutli-CPU test (a four per cent improvement), the rest were identical to the Q9400.

Conclusion

If you already have an AM2+ motherboard then the Phenom II 940 is the upgrade your system deserves. It performs nine to 31 per cent better than the 9950 in most CPU and non-GPU bound gaming tests. However, if you’re choosing between a brand new AMD and Intel PC, things get a little muddier.

Let’s be clear: Core i7 is still king of the hill and Core 2 Quads remain the most energy efficient processors.

Assuming the Phenom II 940, Core 2 Quad Q9400 and Q9450 end up retailing for a similar amount, as AMD predicts, then the Phenom II 940 is generally better value for money. Although the Core 2 Quad Q9400 has a thin lead in gaming, the Phenom II 940 is a bit faster in 2D tasks. Leaked pre-order pricing info suggests the Phenom II 940 may cost as much as a Q9550, in which case Intel is the better buy. Of course, if only the price of DDR3 Ram and X58 motherboards would halve in price, then the Core i7 920 would be a no brainer.

Another issue is ye old cliché, future-proofing. AMD is switching to AM3 motherboards and processors in Q2, which have DDR3 Ram support. You can’t use the AM2+ Phenom II 940 with an AM3 motherboard, but at least you can buy a Phenom setup now knowing your AM2+ motherboard can accommodate future processors. If you go the Core 2 route then you’ll have to chuck the motherboard when you transition to Core i7.

As for overclocking, well, it’s a mixed bag. The Phenom II has much better overclocking capabilities than the original Phenoms, but it’s no better than Intel’s quad cores. The easy way to overclock a Phenom II 940 (just turn up the multiplier, like we did) doesn’t improve 3D performance much. Tweaking the Hypertransport frequency may improve gaming performance a bit (since the GPU can be fed by the CPU a bit quicker), but patience and a good motherboard are essential if you are to have much success.

If we put our pretend shareholder hats on for a minute and consider the manufacturing side of things, AMD seems to be less competitive than Intel. The Phenom II is a 758 million transistor chip with a 258mm² die area, while Core 2 Quads with 12MB L2 cache have two dies measuring 107mm² (in effect 214 mm²) which appears to suggest Intel’s chips use less silicon and are therefore cheaper to make.

There are too many factors to say that’s a certainty – yields, manufacturing process, equipment costs – but it does look like AMD is in for a precarious 2009.

That also means we’re in for an expensive 2009, because the lack of Core i7 competition means we’ll be paying sky-high prices for Intel’s best CPUs and its monopoly is assured.

The good Faster than low end Penryn chips in CPU-specific tasks

The bad Intel chips remain best for gaming. Phenom II has slightly higher power draw than Penryn chips.

The really ugly Intel’s monopoly is here to stay

Bartender’s verdict