New Xeons bring dramatically lower idle power

— 11:07 AM on August 13, 2007

Intel's Xeons have taken quite a bit of market share from AMD's Opterons in the past year or so, and rightly so, thanks to a nice combination of performance and power efficiency under load. Those Xeons have had a notable Achilles' heel, though, in the form of high power consumption at idle. (You can see our numbers from when we measured it, for instance.) The Xeons' high idle power primarily comes from two culprits: the Xeon platform's use of FB-DIMMs and the CPU chips themselves. This fact has left something of an opening for the Opteron, whose place in the data center has been cemented by its overall power efficiency. However, Intel has just announced some changes to its Xeon lineup today that could change the picture dramatically.

The headline news you may see around the web is the official introduction of two new Xeon models, the X5365 and L5335. The quad-core Xeon X5365 runs at 3.0GHz on a 1333MHz front-side bus, and we reviewed it a while back as part of Intel's "V8" media creation platform. This CPU has been shipping exclusively in Mac workstations for some time, but should now be more widely available. The L5335 is a new low-power quad-core processor with a 2GHz clock speed, 1333MHz bus, and a thermal design power (TDP) of just 50W—a product distinctly poised to take on AMD's upcoming Barcelona-based Opteron chips.

The bigger news that you may hear less about is the advent of the new G stepping of chips across the Xeon lineup. These chips are still manufactured using a 65nm fabrication process, but a combination of changes—including the ability to reach lower CPU multipliers and thus lower clock speeds—leads to much lower power consumption at idle for many Xeon models. Here are the numbers Intel presented to us on the reduction in idle power use for its quad-core Xeons:

Clock speed Front-side bus TDP Old idle power New idle power
Xeon X5365 3.00GHz 1333 MHz 120W 50W 25W
Xeon X5355 2.66GHz 1333 MHz 120W 50W 25W
Xeon E5340 2.33GHz 1333 MHz 80W 30W 25W
Xeon E5330 2.00GHz 1333 MHz 80W 34W 34W
Xeon E5320 1.86GHz 1066 MHz 80W 30W 30W
Xeon E5310 1.60GHz 1066 MHz 80W 34W 34W
Xeon L5335 2.00GHz 1333 MHz 50W N/A 24W
Xeon L5320 1.86GHz 1066 MHz 50W 24W 24W
Xeon L5310 1.60GHz 1066 MHz 50W 24W 24W

And for the dual-core Xeons:

Clock speed Front-side bus TDP Old idle power New idle power
Xeon 5160 3.00GHz 1333 MHz 65W N/A 8W
Xeon 5150 2.66GHz 1333 MHz 65W 24W 8W
Xeon 5140 2.33GHz 1333 MHz 65W 24W 8W
Xeon 5130 2.00GHz 1333 MHz 65W 27W 27W
Xeon 5120 1.86GHz 1066 MHz 65W 24W 12W
Xeon 5110 1.60GHz 1066 MHz 65W 15W 6W

Power use at idle drops by as much as 25W per processor—or 50W total in a dual-socket system—for the high-end quad-core Xeons, with smaller reductions for slower CPUs. These improvements may not entirely make up the idle power gap with the Opteron, but they should come fairly close. Given that Intel has the performance lead and double the density of cores per socket, well, let's just say AMD needs to deliver Barcelona now more than ever.

Nevertheless, the G-step Xeons are just a minor marker in Intel's roadmap, whose next major milestone involves 45nm "Harpertown" Xeons and a new "Stoakley" platform designed to complement them.

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