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What's on the bench
The Xeons we have for review represent the best of the 5600 series on one axis or another, and we've tested them in different types of systems as appropriate. The most extreme of the bunch is the Xeon X5680, which has a base clock speed of 3.33GHz and can raise its frequency as high as 3.6GHz via Turbo Boost when the thread count and thermal headroom permit. The X5680's max power and thermal rating, or thermal design power (TDP), is 130W, which puts it on the high end of the power spectrum. As Intel's fastest 2P processor, this model commands a hefty price premium, too. A single X5680 will set you back $1663.

Our test platform for this beast is a relatively large, floor-standing workstation enclosure with a SuperMicro X8DA3 motherboard and a 700W power supply. That combination is comfortably up to the task of cooling and powering a system with a pair of 130W processors.

We should note that, although 5600-series Xeons are billed as drop-in replacements for the 5500-series Xeons before them, at Intel's recommendation, we upgraded the motherboard in this test system rather than using the older version of the X8DA3 used in our Xeon 5500 review. That older X8D3A was pre-production hardware from the early days of Nehalem, so the change was needed for optimal operation. However, Intel tells us many Xeon 5500-based systems should allow for seamless drop-in upgrades to Westmere Xeons. As is usually the case in these scenarios, you'll want to check with your motherboard or system vendor for compatibility information.


Asus' RS700-E6 1U server

The X5680's 130W TDP will probably rule it out of most server installations. Xeons in the 95W power band are more common, and the X5670 is Intel's fastest offering at that TDP. The X5670 runs only slightly slower than the X5680, with a 2.93GHz base clock and a 3.33GHz Turbo peak. Stepping down to the X5670 will give you a nice break on max power ratings, but at $1440, it's not much less expensive.

We've tested the X5670 in an Asus 1U server system, pictured above. We also dropped a pair of Xeon X5570 processors into this system—the prior-gen Nehalem offering at the same frequency and TDP—to see how the two generations of Xeons compare.


The low-power Willbrook server

To many folks, the Xeon L5640 may be the sexiest of these new CPUs. Its six cores run at 2.26GHz and can spool up to 2.8GHz via Turbo Boost, yet this Xeon's TDP rating is a calm and collected 60W. Naturally, that fact makes the L5640 a fantastic candidate for a power-efficient server. You will pay a premium for this sort of power efficiency, though: the L5640 lists at $996 per chip.

Our test system matches a pair of L5640s with a custom motherboard from Intel officially known as the S5500WB—and unofficially code-named Willowbrook. Although this Willowbrook board is based on the same Tylersburg—excuse me, I mean "Intel 5500 series"—chipset as our other Xeon systems, Intel has specifically optimized this board for reduced power consumption. Those optimizations include a carefully tuned voltage regulator design and more widely spaced components intended to permit airflow and reduce the energy required by cooling fans. The firm claims a 32W savings at idle and a 42W savings under load versus its own S5520UR motherboard.


To that potent mix of power-efficient components, we've added six DIMMs of low-power Samsung DDR3 memory. These DIMMs operate at only 1.35V, and Samsung happily touts them as a greener alternative to traditional DDR3 modules.

As you may be gathering by now, this entire platform ought to be quite nicely tailored for low-power operation. To give us a sense of how the enhancements in the Westmere Xeons alone contribute to this system's efficiency and performance, we've tested a couple of quad-core Xeon L5520 processors in this same system. The L5520 has the same 2.26GHz base clock at 60W TDP as the L5640, but its 2.53GHz Turbo max is lower, and its memory speed tops out at 1066MHz.

A competitive imbroglio
As our regular readers will attest, we usually try to test products against their closest competition whenever possible. For the Xeon 5600 series, that competition would most definitely be the latest Opterons from AMD. In order to keep pace with Intel's formidable performance gains in recent years, AMD has elected to double up on the number of chips it delivers in a single package. The resulting processors, code-named Magny-Cours, were formally announced in late March as the Opteron 6100 series. With 12 cores and four channels of DDR3 memory per socket, these new Opterons promise substantial gains over the six-core Istanbul chips introduced a year ago, even though the basic building block is essentially the same hunk of silicon.

Doubling up on chips per socket can be a savvy strategy in the server market, one that Intel itself validated with its Harpertown Xeons back in 2007. Seeking to upgrade performance by raising clock speeds is a tricky endeavor, because it requires increases in chip voltage that can raise power draw exponentially. By keeping clock speeds low, and thus voltages in check, AMD has made room for multiple chips per socket while staying within its traditional power bands. For widely threaded workloads, this approach could pay solid performance dividends.

Several of the Opteron 6100 models look like good matches for the CPUs we're testing. The Opteron 6176 SE with 12 cores, a 2.3GHz core clock, and a 105W ACP rating looks like a plausible rival to the Xeons X5680 and X5670 we have on hand. The 6176 SE's $1386 price tag makes it a close competitor, too. Meanwhile, the Opteron 6164 HE at $744 might well be the closest competition for the Xeon L5640. With 12 cores at 1.7GHz and a 65W ACP, the 6164 HE could make things interesting, at least.

More recently, AMD has announced the Opteron 4100 series, code named Lisbon during its development. These CPU use only a single chip but add DDR3 support like Magny-Cours. The 4100-series Opterons are aimed primarily at compact, high-density server installations, and a bit of mystery surrounds the potential customers for these products. AMD expects the 4100 series to appeal to big web companies that buy large numbers of servers through custom design groups at major OEMs, but it has said not to expect sales figures from that business to become public. Whether such talk foreshadows stealthy success or silent-but-abysmal failure, we do not know.

We do know the 4100 series isn't positioned directly against the Westmere Xeons, by and large. The fastest Lisbon chip is the Opteron 4184, with six cores at 2.8GHz and a 75W ACP, and it lists for $316. At that price, the 4184 competes against the quad-core Xeon X5500 processors that remain in Intel's product portfolio.

Unfortunately, we don't have any of these newer Opterons to test. We have worked with both AMD and Intel for years to make these reviews possible, and both companies have supplied us (and other publications) with samples of their latest products. Initially, this product cycle was no different. We even made a two-day visit to AMD's server group in Texas to talk about the new Opterons a couple of months back, yet we're still awaiting word on review samples. That is, frankly, one reason this review is a little late to publication; we had sincerely hoped to include a head-to-head comparison of the latest CPUs.

Of course, some of the blame for the absence of newer Opterons here lies with us. We should have seen the writing on the wall and pursued other avenues for getting hold of a system sooner, either by working with a server maker or just buying the stuff ourselves. We're still hoping to put the new Opterons through their paces, but we couldn't delay publication of this review any longer. For the time being, we've tested the latest Xeons against the products they replace—and against the older generation of Opterons. That's not our favored outcome, but we should be able to get a good sense of the Westmere Xeons' relative performance, regardless.


Fortunately, we do have an Opteron platform you may not have seen tested in the wild just yet. Tyan was kind enough to supply us with its S8212 motherboard, which is based on AMD's SR5690 chipset, better known as the Fiorano platform. Fiorano is AMD's first attempt to produce its own server platform in quite a few years, and it adds a few critical features to the Opteron's quiver. Among them: support for the HyperTransport 3 and PCI Express 2.0 interconnects, both with higher throughput than the older versions of those standards. Although our Fiorano system doesn't make use of DDR3 memory, it is otherwise comprised of basically the same components as any newer Opteron 4100 system, with the same SR5690 chipset and six-core, 45-nm processors. In this case, we've used Opteron 2435 CPUs clocked at 2.6GHz with a 75W power envelope. The analogous model in the 4100 series would be the Opteron 4180, which shares the same clock frequency and max power draw rating.

For what it's worth, we built our Fiorano test rig using the same type of floor-standing enclosure and power supply as our Xeon X5680 box, so comparisons between those two should be reasonably direct, if something of a mismatch.

We have a power-optimized representative from the Opteron fold, as well, in the form of a 1U server with an efficient 650W PSU and a pair of Opteron 2425 HE processors. The Opteron 2425 HE is a six-core, 2.1GHz part with a 55W ACP. This system is based on an older SuperMicro H8DMU+ motherboard with an Nvidia chipset. Although it lacks a few new features, I believe this board is more power-efficient overall than most existing Fiorano-based mobos, which is why we chose to test the Opteron HEs on it.