Intel boosts the high-end desktop with its Broadwell-E CPUs

More cores, more threads, more money

Intel's Broadwell-E high-end desktop CPUs are probably one of tech's worst-kept secrets by this point. The wraps are officially coming off the company's biggest, baddest fifth-generation Core CPUs today, so we can finally tell you all about them and the changes within. Compared to Haswell before it, Broadwell-E's underlying microarchitecture delivers about a 5.5% higher instruction throughput per clock cycle thanks to a combination of microarchitectural tweaks and new instructions. These new "Extreme" chips are fabricated on Intel's 14-nm tri-gate process, the "tick" to Haswell's 22-nm "tock."

The top-end Broadwell-E chip, the Core i7-6950X, adds two more cores, four more threads, and 5MB more last-level cache to the complement of the previous king of the hill, the Core i7-5960X—all in the same 140W thermal envelope. Those changes mean that builders can now put ten cores, 20 threads, and 25MB of cache in one LGA 2011-v3 socket. As we've come to expect from Intel's highest-end desktop parts, all Broadwell-E CPUs are unlocked for easy overclocking, too.

If those were the only changes in these chips, we'd have a fairly simple story to tell today. The refinements don't end there, though. Intel is introducing a new technology called Turbo Boost Max 3.0 with Broadwell-E. This tech is a further evolution of the Turbo Boost dynamic overclocking feature introduced with Nehalem Core i7s back in 2008 and its more aggressive second iteration in 2011's Sandy Bridge CPUs.

Turbo Boost Max 3.0 is meant to mitigate the single-threaded performance deficit that the Extreme chips often exhibit in comparison to Intel's higher-clocked quad-core chips like the Core i7-6700K. Turbo Boost Max 3.0 (or TBM 3.0 for short) works by finding the core with the most potential frequency overhead, pushing its clock speed to the limits, and prioritizing workloads to run on that core.

To use Turbo Boost Max 3.0, Broadwell-E owners will need to install a driver from Intel that enables the feature. This driver also comes with a basic utility that lets users control some parameters about how TBM 3.0 should behave. By default, the TBM 3.0 driver will prioritize the application with focus, but users can also create a list of applications that should always be run on the chip's fastest core.

We're still working up a full Broadwell-E review as of this writing, but we ran some tests in Cinebench to get a rough idea of how much Turbo Boost Max 3.0 can help speed up single-threaded tasks on the Core i7-6950X. Switch between the single- and max-threads results from Cinebench using the buttons below the graphs. (No, there's not a Core i7-6700K represented in these results, but that chip is only about 3% faster than a Core i7-4790K in single-threaded Cinebenching.)

Long story short, TBM 3.0 does appear to seriously, well, boost the performance of tasks that rely on the strength of a single thread. We don't usually see Intel's Extreme CPUs track the company's higher-end quad-core chips so closely in single-threaded tasks. As one might expect from a chip with two extra cores and four extra threads on the Core i7-5960X, the Core i7-6950X establishes a whole new league of performance when all of its cylinders are firing, too. Good grief.

We also fired up AIDA64 to get a sense of just how much TBM 3.0 is pushing clocks on the best-performing core on our chip. We found that with or without TBM 3.0 enabled, one of the cores on our chip was hitting 4GHz peak Turbo speeds with the Cinebench 1T test running. The difference that TBM 3.0 makes appears to be one of duration. With the feature active, the core sustained that clock speed for the majority of the test, while turning it off caused the core to spend only a little bit of time at its peak speeds. Interesting.

You may have already guessed as much, but the X99 platform will continue to underpin these next-generation Extreme CPUs. That means we still get four channels of DDR4 memory, scads of SATA ports, and enough PCIe lanes to run even the craziest multi-GPU setups that builders can dream up—so long as they pay up for the right CPU, anyway. Existing X99 motherboards should work with Broadwell-E chips with nothing more than a firmware update. Intel is bumping officially-supported DDR4 speeds up to 2400 MT/s with Broadwell-E, but that's about the only major platform change worth noting. You can read more about this platform in our Haswell-E review.

Get that credit card ready
To get the two extra cores and four extra threads that the top-end Core i7-6950X provides over the Core i7-5960X, buyers will have to pony up a whopping $1723. Intel has never shied away from charging a premium for its most-extreme Extreme CPUs, but those chips have consistently sold for about $1000 even as their core and thread counts have grown over the years. Broadwell-E breaks that tradition with a top-end chip that costs as much by itself as an entire high-end PC from our latest System Guide. Let that sink in for a moment.

With this new price structure, the Broadwell-E lineup beneath the Core i7-6950X looks remarkably similar to Haswell-E before it. For $1089, buyers get the same eight cores and 16 threads in the Core i7-6900K that they got with the Core i7-5960X, so that level of CPU resources isn't getting any more accessible with these new chips. Turbo Boost Max 3.0 looks like it could be a nice improvement, to be sure, but the value proposition of a $1000 CPU was already muddy. Broadwell-E doesn't do much to make that prospect any more appealing.

In the $400-$600 range where we usually begin feeling comfortable recommending Extreme CPUs, builders get two options. At $434, the Core i7-6800K gives buyers 28 PCIe lanes, a 3.4GHz base clock, and a 3.6GHz Turbo speed. We're no happier with Intel's decision to hobble this CPU's PCIe connectivity than we were when the Core i7-5820K first showed its face, but Intel seems to have settled on tweaking this particular knob in exchange for giving buyers a chip at this price point. Builders who want to take full advantage of all 40 lanes of PCIe connectivity on the X99 platform will need to cough up about $200 more for the $617 Core i7-6850K. That chip gives builders a 200MHz boost in base and Turbo clocks over the Core i7-6800K for their trouble, too.

Conclusions—for now
All things considered, Broadwell-E chips appear to continue the slow-but-steady pace of improvement we've come to expect from new CPU generations these days. For single-threaded tasks, Turbo Boost Max 3.0 appears to cleverly make up some of the ground that newer chips have gained through architectural improvements by letting these CPUs clock their best-performing core to the sky when it's needed. That extra single-threaded oomph takes a little bit of the edge off spending tons of money on a chip that's not built on Intel's most recent architectural generation. If you were already considering building a Haswell-E system, there's no reason to favor those chips over the Broadwell-E CPUs launching today.

It's disappointing that Intel is breaking the cycle of delivering more chip for the same money as it has with past generations of Extreme CPUs, though. Given that AMD hasn't updated its highest-end desktop CPUs in nearly four years, we're guessing that Intel is establishing a new pricing tier for its beefiest Broadwell-E chip mostly because it can.

If you need all the cores and threads the Core i7-6950X offers, our preliminary results suggest it's a winner. If you don't, though, the $1729 you'll shell out for that chip builds a heck of a PC with a Core i7-6700K inside. The top-end Skylake chip's four cores and eight threads, running at 4.0GHz base and 4.2GHz boost speeds, will probably offer more than enough performance for most people at a price that's not as stratospheric as the top of Taipei 101. Still, the i7-6950X appears to set a new high-water mark for what Intel's Extreme desktop processors can do, and that's always exciting to see at any price.

Tags: CPUs

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