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Ivy Bridge-E and LGA2011 in Detail

To emphasize the premium status of the desktop LGA2011 platform, Intel offers a limited CPU model range for it. The Ivy Bridge-E series announced some time ago only includes three models:

These processors replace the earlier Sandy Bridge-E products and come at the same prices. The Core i7-4960X Extreme Edition becomes the flagship model instead of the Core i7-3970X. The Core i7-4930K replaces the midrange Core i7-3930K. As for the Core i7-4820K, this quad-core CPU is somewhat more expensive than its predecessor Core i7-3820 because it’s got the letter K in its name. In other words, the junior model now features an unlocked frequency multiplier, just like its senior cousins. It is still about $15 or $20 cheaper than the Core i7-4770K, the top-of-the-line Haswell-based LGA1150 model, which is reasonable considering the older microarchitecture employed in the Core i7-4820K.

The transition of the LGA2011 CPUs to the Ivy Bridge-E design has had but a little effect on their specs (see the table above). The number of execution cores, Hyper-Threading support and L3 cache amount are the same as with their predecessors. As for the clock rates, the Ivy Bridge-E CPUs have got 100 to 200 MHz faster. However, the Turbo frequency is limited to 4.0 GHz for the Core i7-4960X, exactly as for the Core i7-3970X. Now Intel has two desktop CPUs capable of working at 4 GHz whereas the Haswell-based series is limited to 3.9 GHz in Turbo mode.

Considering the overall similarity between the Sandy Bridge-E and Ivy Bridge-E designs, it is remarkable that the new CPUs have a special 6-core semiconductor die. The previous generation was based on the 8-core die of server CPUs with two cores disabled but now the die only contains six physical computing cores. As a result, the Ivy Bridge-E has a considerably smaller die than the Sandy Bridge-E: 257 vs. 435 sq. mm. Of course, the 22nm technology contributes to the miniaturization as well, but the total number of transistors has also been reduced, from 2.27 to 1.86 billion.

The removal of the two unneeded cores from the die might have been accompanied with an increase in the cache memory amount, yet the L3 cache is still only 15 megabytes in the senior CPU model. The midrange and the quad-core junior models have 12 and 10 megabytes of L3 cache, respectively. The only memory-related innovation concerns the top frequency supported officially. The Ivy Bridge-E is declared to be compatible with DDR3-1866 (with one module per channel) although such CPUs can work with faster memory modules in practice.

The TDP of the senior Ivy Bridge-E has been reduced. The Core i7-3970X used to have a TDP of 150 watts whereas the Ivy Bridge-E series have a TDP of 130 watts.

The fact that the new LGA2011 CPUs are fully compatible with the old platform, announced two years ago, is both good and bad. It is good to have an opportunity to easily upgrade your old computer with a new CPU. But it is bad that the only LGA2011-compatible chipset, Intel X79, is rather outdated already.

The chipset doesn’t support USB 3.0 and has only two SATA 6 Gbit/s ports. It means that mainboard makers have to add third-party controllers to implement these interfaces, which has negative consequences in terms of price and compatibility. The X79 leaves no alternatives, though.

And still, the opportunity to install a completely new CPU onto a 2-year-old mainboard seems to be most attractive to us. The LGA2011 platform suggests this upgrade scenario as old LGA2011 mainboards become fully compatible with the Ivy Bridge-E CPUs after a simple BIOS update with only one and very odd exception – Intel’s own mainboards. Intel has been shutting down its mainboard business and doesn’t plan to release new firmware for its LGA2011 products. So, unfortunately, owners of such rather good mainboards as Intel DX79SI, DX79SR and DX79TO are left without support for the new CPUs.

The long lifecycle of the LGA2011 platform is not its only advantage. Besides offering more computing cores than top-end LGA1150 CPUs, the Ivy Bridge-E processors provide more PCIe lanes and feature a unique quad-channel memory controller.

As opposed to LGA1155 and LGA1150 CPUs that offer 16 PCIe lanes for the graphics subsystem, LGA2011 CPUs offer 40. This is true for both Sandy Bridge-E and Ivy Bridge-E generations, but the newer models support PCI Express 3.0. The latter standard was implemented in the Sandy Bridge-E but lacked official validation, so Nvidia's GeForce cards worked in PCIe 2.0 mode by default and the user had to do some manual setting-up to make them work in PCIe 3.0 mode. There should be no such problems with the new LGA2011 CPUs. Moreover, in the latest driver versions Nvidia has unlocked PCIe 3.0 for Ivy Bridge-E processors as well.

The memory controller hasn't changed. Borrowed from server products, its behavior isn’t always rational on desktop platforms. Like their predecessors, the Ivy Bridge-E processors work with four memory channels, which ensures a peak bandwidth of 60 GB/s with DDR3-1866 SDRAM. However, the entire bandwidth can only be utilized in case of multithreaded data access. When it comes to single-threaded access, the memory controller turns out to be worse in terms of bandwidth and latency than the dual-channel controller of LGA1155 and LGA1150 processors.

Considering these peculiarities, Intel emphasizes the fact that the updated LGA2011 platform is not a versatile solution. There are three spheres where its use is optimal: multimedia content authoring and processing, extreme overclocking experiments, and uncompromising gaming with multi-GPU configurations. We can note a change in the market positioning: the LGA2011 is not promoted as the best choice for each and every gaming computer anymore.

 
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