Benchmarks: AMD's Phenom II

AMD's Phenom II processor is designed to boost the company's presence in the desktop market. But how does it fare against Intel's latest Core i7 (Nehalem) chip?

Intel has been manufacturing desktop processors using the 45-nanometre (nm) feature size since November 2007, but it wasn't until over a year later that rival AMD began to distribute chips manufactured using this process — currently the most advanced in mainstream processor production. Shanghai processors for the server market have been produced at AMD's Dresden factory since November 2008. AMD was delayed because of problems with 45nm manufacturing and Silicon-On-Insulator (SOI) technology. These difficulties have now been solved and the desktop variant, Phenom II, is ready for market.

With the move to 45nm, AMD can now clock the Phenom II processors at significantly higher speeds than their 65nm predecessors. At 3GHz, the Phenom II X4 940 is the fastest variant (its Phenom equivalent ran at 2.6GHz). Despite higher clock speeds and an increase in transistor count to 758 million (from 463 million) by doubling the Level 3 cache, the new CPU's power consumption remains unchanged at 125W.

The Phenom II is pin-compatible with its predecessors, so all that's needed to upgrade to Phenom II is a simple BIOS update of an AM2+ socket motherboard. Most of the larger motherboard makers — including Asus, Gigabyte and MSI — published compatibility lists in December. Along with the Phenom II X4 940, a 2.8GHz 920 model is also available.

Test models and platforms
For all the tests of AMD's new processors, we used the MSI DKA790GX Platinum motherboard with an AMD 790GX chipset. The Intel Core 2 Duo E8500 and Core 2 Quad Q9550 processors operated on a Gigabyte GA-X38T-DQ6 motherboard, while the Nehalem Core i7 920 chip used a Gigabyte EX58-DS4 board.

For main memory, the AMD systems used two 1,066MHz OCZ 2GB DDR2 modules. These chips do not adjust themselves automatically in the BIOS to the frequency specified by the manufacturer, but have to be manually set to run at the higher speed. We also had to increase the voltage to 2.2V.

The Intel systems with Core 2 Duo and Core 2 Quad CPUs used two 2GB Aeneon DDR3 modules running at 1,333MHz, while the Nehalem system used three 2GB Aeneon modules running at Intel's recommended DDR3 speed of 1,066MHz. For comparative purposes, the differing main memory sizes of 4GB for the Core 2 Duo, Core 2 Quad and Phenom II systems against the Core i7 920 with 6GB had no bearing on the test results.

We used an ATI Radeon HP 4870 graphics card with the 8-561-3-081217a-73402 driver and a Raid-0 array of two 250GB Western Digital disks for storage. The systems ran Windows Vista 64 SP1.

Everest: Memory and arithmetic performance
Memory tests provide our first insight into the efficiency of the test systems. Thanks to its integrated memory controller, which has a three-channel memory controller, Intel's Nehalem Core i7 920 processor records the best memory performance by some distance. The new AMD processors   deliver slightly lower throughput rates than Intel's Core 2 and Core 2 Quad chips.

Intel's quad-core processors come out top in the Everest FPU (floating-point unit) tests. AMD's Phenom II 940 performs well in the FPU Mandel and Sin-Julia tests against the Core 2 Quad 9550.

The AMD processors are competitive in the CPU tests. The PhotoWorxx and the CPU Zlib tests put a big load on memory, so it's no surprise that the Phenom II chips score well compared to the Core 2 Quad 9550 with its frontside bus. However, the Phenom IIs trail behind Intel's newer Core i7 920.

3D performance: Farcry 2, Crysis, 3D Mark Vantage
The 3D Mark Vantage gaming benchmark provides three results. The CPU score shows how well the processors perform physics calculations, while the GPU score measures graphics card performance. The 3D Mark score gives the overall score from both the individual tests.

In the CPU test, the Intel chips are clearly some way ahead of the AMD competition, but in the GPU score the differences are less pronounced. Overall, the Intel chips come out narrowly ahead.

3D Mark Vantage is an artificial test that says little about practical performance, unlike genuine 3D games. When running Fear, the AMD chips show what they are capable of, although they are outstripped in Crysis and Farcry 2 by the Intel systems. It's interesting that in this area the dual-core E8500 can match the quad-core chips for pace — 3D games are obviously not designed to exploit all the features of the quad-core architecture.

Application performance: encryption, compression, internet
TrueCrypt and 7-Zip are designed to extract optimal performance from the CPU's arithmetic and logic units. The dual-core Core 2 Duo E8500 processor cannot keep up with the quad-core chips. When it comes to compression and decompression with 7-Zip, Intel's Core i7 920 puts on the best show by some margin — twice the performance of the comparatively slow Core 2 Duo E8500. The Phenom II processors also make the dual-core look old. In the TrueCrypt benchmark, the Phenom IIs even match or outstrip Intel's latest Core i7 920.

Modern internet applications make much use of JavaScript and run faster on quad-core processors than on dual-core chips (see the SunSpider Javascript test results). However, for simple HTML pages the dual-core processor is faster than the quad-core chips.

Rendering, MP3, video, image handling
The quad-cores stand out in the Adobe Media Encoder CS4 test. As is frequently the case, the fastest processor in this test is Intel's Core i7 920. The Phenom II X4 940 keeps up with the quad-core 9550, but it's a different story in the iTunes 8.02 test. The Apple program uses only two CPU cores under Windows Vista, so the E8500 encodes MP3 data fastest because it has the highest clock frequency of all the CPUs on test. Under Mac OS X, iTunes does not suffer from this restriction.

In the Cinebench test, the Core 2 Duo has no chance against the quad-cores. Predictably, the E8500 records the best result in the single-CPU test because it has the highest clock speed. However, the main Cinebench rendering test uses all the CPU cores, and the Core 2 Duo just cannot keep up. The fastest chip is the Core i7 920.

The image-handling tests show the advantages that quad-core processors can offer. Again, the Core 2 Duo trails in last some way behind the field. The Phenom II X4 940 and Core 2 Quad 9550 offer broadly similar performance, with the edge just going to the Intel chip. Jalbum and Paint .NET both support multi-threading, so it's not surprising that Intel's Core i7 920 is a clear winner. That picture changes with Autopano Pro, which also supports up to eight threads — although that feature currently offers no practical advantage. On the contrary: this beta program runs slower using all eight threads than it does with just four.

Power consumption and conclusion
The new AMD quad-core Phenom II's power consumption profile is impressive. In idle mode it draws the least power of all the high-end processors tested. Under full load its consumption is in line with the competition.

Two- or four-core?
In testing high-end quad-core processors, the question that naturally arises is to what extent modern applications capitalise on the additional cores. In other words: when do quad-core chips start to pay their way? With 3D games, the quad-cores offer hardly any advantages over dual-core chips. In fact, in this area the 3.16GHz Core 2 Duo E8500 is often faster than the quad-core processors. The quads' true strengths start to show in the compression and decompression of files in the 7-Zip test, and in encryption with Truecrypt 6.1a.

The quad-core chips also show that their arithmetic and logic processing gives them a clear edge over the dual-cores when handling video with Adobe Media Encoder CS4 and when rendering with Cinebench.

Against the 3.16GHz Core 2 Duo E8500, the 2.66GHz Core i7 920 registers twice the performance in the Cinebench test. Today's internet applications make much use of JavaScript, and the SunSpider Javascript test shows that the quad-core processors are also faster in this area than the dual-cores. The underlying point is that modern applications are increasingly designed to exploit the abilities of quad-core processors. iTunes alone represents the inglorious exception in the multimedia arena, supporting only two threads under Windows Vista. Under Mac OS X, iTunes fully exploits all four cores.

Conclusion
Although the naming of the Phenom II X4 with the 920 and 940 model numbers echoes Intel's Core i7 naming convention, that's where the similarity with the Nehalem chips ends. The Core i7 supports the processing of eight threads simultaneously. In many tests the Intel chips demonstrate this advantage fully, and even in benchmarks where the Nehalem architecture is not fully exploited, the 2.66GHz Core i7 920 outperforms the 3GHz Phenom II. In the whole set of ZDNet benchmarks, the only test where the Phenom II delivers a slightly higher score than the Core i7 920 is Truecrypt 6.1a. Even here there's a caveat. For the purposes of this test, the Core i7's automatic overclocking, or turbo mode, was deactivated. If it was turned on, the chip's performance would have improved by several percentage points. Although the Core i7 920 has a nominal clock speed of 2.66GHz, in practice it runs at 2.83GHz.

The Core i7's performance may be in another league, but then so is its cost. Australian online technology retailers are offering the Core i7 920 from anywhere between AU$600 and AU$1100, the 940 at between $1100-$1250 and the 965 at around $2500-$2900. However the Phenom II X4 940 in Australia retail online for between AU$350 and AU$410. With Core i7, you must add the additional cost of acquiring a significantly more expensive motherboard.

In AMD's Reviewer's Guide, the Phenom II processors are described as direct competitors to the quad-core Q9400 and Q9200 models. That positioning is clearly more realistic than the Phenom naming convention, which might suggest that the Core i7 is the real competition. The benchmarks suggest that even the 2.83GHz Core 2 Quad 9550 is competitive with the 3GHz Phenom II X4 940, although not in image handling (as demonstrated by the Jalbum, Autopano pro and Paint .NET tests).

AMD plans to deliver Phenom II processors with support for DDR3 RAM this spring. However, even this change is unlikely to significantly change the performance picture.