Intel Core i9-7960X review: It beats Threadripper, but for a price

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Whether the Core i9-7960X was always part of Intel’s plans for the high-end desktop (HEDT), or whether it was haphazardly rushed to market to combat AMD’s bullish Threadripper platform, one thing is clear: Intel once again has the fastest slice of silicon on the market. With 16 cores and 32 threads, matching AMD’s flagship Threadripper 1950X, the i9-7960X is an unashamedly over-the-top processor that breaks benchmarking records and powers through heavy production tasks.

But a processor is more than its raw number crunching prowess. Threadripper raised the bar for HEDT with the rich, consumer-friendly X399 platform, which offers a full set of features without spurious lockouts. More importantly, AMD doesn’t charge through the nose for it. The Threadripper 1950X features 16C/32T and costs £950/$1,000. Intel’s Core i9-7900X offers just 10C/20T for the same price. With the exception of gaming, the 1950X is a much more powerful processor.

Unfortunately, despite the strong competition, Intel isn’t yet willing to compete on price. The i9-7960X costs a whopping $1,700/£1,700—and while it might be faster, it certainly isn’t £700 faster. That’s not to mention that Intel continues to use a weak thermal material to mount its CPU heat spreaders, instead of the superior solder that AMD uses. It makes the i9-7960X a bear of a chip to overclock and noisy at stock without suffering serious thermal issues.

Ultimately, the i9-7960X raises the same question as the i9-7900X: Are you willing to pay for the best performing silicon on the market? Or is Threadripper, which offers most of the performance at a fraction of the price, good enough?

Skylake-X Redux

Intel’s X299 platform, to which the i9-7960X belongs, launched with more of a whimper than a bang. The CPU range, which starts with the questionably useful £240, quad-core i5-7640X and is topped by the $2000, 18C/36T i9-7980XE, is a confused mess of different CPU architectures and platform features.

The cheapest quad-core i5-7640X and i7-7740X chips (the latter of which does at least include hyper-threading), only feature 16 PCIe lanes and dual-channel memory, thanks to being based on the the same mainstream Kaby Lake architecture as the 7700K and 7600K. Even more expensive eight-core chips like the i7-7820X only feature 28 PCIe lanes.

This isn’t a problem for the i9-7960X, which features the full complement of 44 PCIe lanes (and can thus take advantage of the X299 platform’s multitude of memory slots, PCIe slots, and I/O). But even that can’t match the 60 offered by AMD’s Threadripper, which allows for some serious three- and four-way graphics card setups with room to spare for PCIe NVMe storage. You even get the full complement of 60 PCIe lanes on the £500/$550 8C/16T 1900X.

Still, 44 PCIe lanes remains a substantial uplift over the paltry 16 offered by Kaby Lake. There’s also official support for quad-channel DDR4-2666 memory (with most motherboards offering support for higher speeds up to 4000MHz), and naturally every X299 CPU is unlocked for overclocking. Unlike Threadripper, however, ECC support remains a Xeon-only feature.

Where the i9-7960X differs from Intel’s cheaper X299 chips is with its hefty 165W TDP, and lower clock speeds. That additional 20W over the 10C/20T i9-7900X might not sound like much, but it makes a substantial difference to power consumption and heat, particularly when overclocking.

Meanwhile, i9-7960X’s base clock of 2.8GHz is lower than other X299 chips (bar the i9-7980XE), as is the all-core boost, which reaches just 3.6GHz. AMD’s Threadripper struggles to get much past that when all 16 cores are under load, too, but it’s notable that Intel doesn’t have a clock speed advantage over AMD, at least without overclocking.

Intel Turbo Boost Max 3.0 returns to help pick up the pace when fewer cores are needed. Turbo Boost Max 3.0 picks out two favoured cores—those deemed to have the best thermal and voltage characteristics—and uses them to speed up single-threaded workloads by around 100MHz to 200MHz (a similar approach is taken by AMD’s XFR boost). Unlike with Broadwell-E, support for Intel Turbo Boost Max 3.0 is baked into Windows 10, negating the need to manually download drivers.

It’s also worth noting that Intel’s Virtual Raid On CPU (VROC) feature—which allows you to link several M.2 NVMe SSDs in a bootable virtual RAID either via on-board M.2 slots, or via an expansion card—remains locked to RAID 0 out of the box. Those wanting to run other types of RAID need to purcahse a small VROC dongle for around £100/$100, which sits in its own slot on the motherboard.

While the market for such a setup is small, that you have to pay extra for it on an already expensive platform is price gouging of the highest order. Threadripper didn’t support bootable NVMe RAID at launch, but an update that enables RAID 0, 1, and 10 for up to 10 drives is now availiable. Best of all, it’s free.

MCM or monolithic?

Like the i9-7900X before it, the i9-7960X is based on the same 14nm FinFET Skylake-SP architecture of Intel’s Xeon server and workstation chips, which feature a new AVX-512 instruction set (up from 256-bit-wide AVX) and a new cache hierarchy. Intel has also dramatically redesigned the way each core exchanges data with another, introducing a mesh topology.

I won’t get into all the details of the tech here (check out the i9-7900X review for a deeper dive), but compared with the old ring bus method of exchanging data between each CPU core, the mesh topology promises to be much more efficient. The side effect is that some multithreaded software optimised for a ring bus may perform slightly slower on Skylake-X, but these applications are few and far between.

What’s more interesting is how Intel has used this mesh topology to construct its multicore CPUs compared to AMD. Intel uses its mesh topology to create a single, monolithic die that contains all 16 cores. Theoretically, since all the cores are on the same die—and because Intel can run the mesh at a solid clock speed, regardless of memory timings—data exchanged between each core is quick and consistent.

The drawback is scalability. The more cores Intel crams into a single die, the larger it becomes, the more costly it is to produce, and the hotter it gets. By contrast, AMD has opted for a multichip module (MCM) design for Threadripper. Theadripper is essentially two eight-core Ryzen dies (which are actually just two four-core dies) thrust together onto the same CPU package, and linked together via AMD’s Infinity Fabric tech.

While Infinity Fabric does rely on fast DDR4 memory clocks to function at its best, the benefit of the MCM design is that it’s far easier to scale to more cores (Epyc, the server CPU Threadripper is based on, features 32 cores) while maintaining reasonable thermals and clock speeds. Threadripper doesn’t run cool by any means. But the i7-7820X takes heat, and power consumption, to worrying new heights.

Listing image by Mark Walton

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