Intel Core i9
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We’re reviewing the first Core i9 chip – Intel’s 10-core Core i9-7900X – as a veritable CPU storm looms. Sure, Core i9 blew in as the most powerful CPU the company has ever sold to consumers, and it’s currently the fastest Core-series CPU available. But an ill wind is blowing: AMD’s Ryzen 5 and Ryzen 7 chips offer stiff competition in the low end, while its massive 12- and 16-core Threadripper CPUs loom on the high end. Here, we walk through some of the under-the-hood issues directly related to performance, and then we’ll dive into the benchmarks.
Core i9, under the hood
Core i9 is the first new ‘Core i’ Intel has introduced in 10 years. The company guarded the secret so closely that it even intentionally mislabelled the chips (including our review sample) as ‘Core i7’ to throw off leakers. In fact, the review sample you see here still identifies itself as Core i7 rather than a Core i9.
Like most major Intel launches, the Core i9 family represents a new platform, not just a new CPU, which means a new chipset, the X299, and a new socket, the LGA2066, all incompatible with previous CPUs.
The new platform also does something no previous one did by unifying two CPU families. Before today, if you wanted the company’s latest Kaby Lake core, you had to buy a motherboard using the LGA1151 socket. And if you wanted to buy, say, a 6-core Skylake CPU such as Intel’s Core i7-6800K, you had to buy an LGA2011 V3-based motherboard.
With X299 and LGA2066, you can now pick your poison, because the platform encompasses everything from a 4-core Core i5 Kaby Lake CPU to an 18-core Core i9 Extreme Edition, which is a Skylake CPU. For clarity’s sake, the Kaby Lake CPUs, also called Kaby Lake-X, are the Core i5-7640X and the Core i7-7740X. The rest of the Core i7 and Core i9 CPUs are Skylake, collectively called Skylake-X.
This union has been greeted with some confusion and trepidation. It’s likely that X299 motherboards will be expensive. Some are rightly wondering who would buy a £350 motherboard to install a £250 CPU.
Intel’s motives for the Kaby Lake-X may actually be a nod to the overclocking sports. Unlike LGA1151-
socketed Kaby Lake chips, Kaby Lake-X chips have no integrated graphics capability. In fact, we’ve been told the chips physically have no IGP on the die at all. This allows the two Kaby Lake-X chips to overclock potentially far higher than the LGA1151 versions. At the recent Computex show in Taipei, in fact, Intel said a record was set for the highest overclock of a Kaby Lake chip, and it was on X299.
In a perfect world, we’d all have 18-core CPUs, but the truth is there are those who buy cheap CPUs on nice motherboards. Kaby Lake-X is for you. PCIe rationing Still, having Kaby Lake-X and Skylake-X on the same socket is bound to create confusion. Exhibit A is the PCIe rationing. With the Core i9-7900X, for example,
you get quad-channel memory support and 44 PCIe Gen 3 lanes directly from the CPU. If you were to drop a Core i7-7740K into the same build, the motherboard drops down to dual-channel memory support and, perhaps worse, the PCIe lanes drops down to 16 lanes because the Kaby Lake core doesn’t support more. That means some of the slots on a motherboard would fall back in performance or be completely disabled.
While Kaby Lake-X’s 16-lane limit is due to the CPU’s design, Intel dials back PCIe lanes on Skylake-X intentionally. Rather than the 44 lanes the 10-core version gets, the 6-core and 8-core versions of Skylake-X get just 28 lanes. From what we understand, there’s no technical reason for it, just “market segmentation,” which is a business school way of saying, “so we can charge you more.”
Even more controversial than PCIe rationing is Intel’s VROC, or Virtual RAID on CPU. It’s a nifty feature on Skylake-X that allows a user to configure up to 20 NVMe PCIe drives in RAID into a single bootable partition. The problem? It seems that Intel intends to charge more money for the feature. Details haven’t been released, but vendors have told us they believe RAID 0 would be free, RAID 1 to cost around £99, while RAID 5 and RAID 10 could cost around £299. You’ll get a hardware dongle that unlocks the feature.
It gets worse: VROC will work only with Intel SSDs and pricier Skylake-X parts. If you buy Kaby Lake-X, you’re shut out. VROC also applies only to PCIe RAID that runs directly through the CPU’s PCIe lanes.
X299 still supports various RAID 0,1, 5, 10 through the chipset, but the chipset RAID won’t touch the performance you get from VROC.
How Core i9 changes Skylake
Once you’ve got beyond the platform confusion and controversy, there’s a reward. The Skylake-X chip itself is indeed something to admire, because it’s built unlike any previous high-end Intel consumer chip.
Previous ‘enthusiast’ or ‘extreme’ CPUs have mostly been the same. That is, a 4-core Haswell Core i7-4770K wasn’t all that different from an 8-core Haswell-E Core i7-5960X except for the support of quad-channel RAM.
With Skylake-X, Intel breaks from tradition, with some major tinkering under the hood. The most
noticeable is an increase in Mid-Level Cache (MLC), or L2 cache: Intel has quadrupled it to 1MB per core, up from 256MB in last year’s Broadwell-E and the majority of Intel’s CPUs. The Last-Level Cache (L3) actually gets smaller, with 1.375MB per core versus the 2.5MB of the previous Broadwell-E chip, but Intel compensates with the larger MLC and also the use of a non-inclusive cache design. Compared to the inclusive design in Broadwell-E, which might keep data that’s not needed, non-inclusive cache attempts to track what should be in the cache so it can more efficiently use the available space.
Intel also ditches the ring bus architecture it has used for several years (including Kaby Lake and Skylake) for a new mesh architecture. If you think of a quadcore CPU as four homes connected by a bus line that
makes stops at each home, it’s perfectly fine until you add, say, 12 or 18 homes to the community. You could connect two bus lines together, but that still isn’t as fast as simply driving from one home to the next, which is what the new mesh architecture does.
Intel’s use of a mesh design clearly puts it on a better footing to compete with Threadripper, as more and more cores are added to CPUs. AMD’s Ryzen series uses something it calls an Infinity Fabric, which is essentially a super-high-speed mesh network.
The last feature worth noting is the improved Turbo Boost Max 3.0. This is the feature wherein Intel identifies the ‘best’ CPU core at the factory and gives it a little more boost speed. With Broadwell-E CPUs, only one core was chosen. With Skylake-X, two cores are identified as the ‘best’ and allowed to run a couple of hundred megahertz faster.
Intel sent us the Core i9-7900X in an Asus Prime X299-Deluxe motherboard. We ran the test bed with the Anniversary Update build of Windows 10. Yes, we know, the world has moved on to the Creators Update, but in order to compare it with past CPUs we stuck with this earlier build.
All of the systems (except where noted) used a GeForce GTX 1080 Founders Edition, 32GB of DDR4/2133 RAM, and HyperX 240GB Savage SATA SSDs. For our Adobe Premiere CC 2017 test, the source project and the target drive used a Plextor M8pe PCIe SSD in all but the Core i5 and the Ryzen 5 CPUs. This exception is due to a problem with the Ryzen 5’s
motherboard, which failed to recognize the Plextor drive. A Samsung 960 Pro NVMe SSD was swapped in.
Where we sourced from our previous tests, those tests used the same Nvidia drivers, the same OS, and the same hardware that we used for this Core i9-7900X review. We did, however, decide to update the test bed for the original 10-core Broadwell-E Core i7-6950X. That test was originally conducted on a very early Asrock X99 motherboard that didn’t fully support Intel’s new Turbo Boost Max 3.0 technology. This time around, we used the same Asus X99-Deluxe II that we used for testing the two Broadwell-E chips.
Our first test is Maxon’s Cinebench R15. It’s a free benchmark based on the same rendering engine used in Maxon’s Cinema4D product. It scales well with core count and frequency and is pretty much a pure CPU test. The results speak well for the 10-core CPUs when compared to the 8-core parts. Even though we’re increasing thread count by only 22 percent, we’re seeing almost a 30-percent increase in performance.
The difference between the 10-core Broadwell-E Core i7-6850X and the 10-core Skylake-X Core i9-7900X is less than expected. According to Intel, you might see up to a 10 percent difference in multithreaded tasks and up to 15 percent in single-threaded tasks when compared to the Broadwell-E 10-core. In Cinebench, we’re seeing just about 3.5 percent.
What changed? The motherboard. What we’re likely seeing is a result of more than a year of tuning
by Asus of its X99 platform. It just pushes the CPU far harder and far faster than the first motherboard. Our initial review of the CPU in this test gave it a score of 1,792, which is quite a bit off from the 2,107 we’re seeing from it now. Other initial reviews put the chip in the low-1,800s. If that score remained true, Skylake-X would be almost 20 percent faster than Broadwell-E.
We also ran Cinebench R15 limited to just a single thread. Because the vast majority of applications and games still rely on a single thread, the performance here is just as important as it is on multithreaded tests. The 10-core Broadwell-E now drops back a few spots, as its clock speeds can’t keep up with the 10-core Skylake-X chip’s. You can also see that the CPUs with
the higher clock speeds move ahead of the 6- and 8-core chips. All except for the 10-core Core i9-7900X.
Large 8- and 10-core chips have had trouble keeping up with the spry quad-cores in high clock speeds. Intel started fixing that in Broadwell-E, but if this Cinebench result holds true, Skylake-X has the potential to hang with Kaby Lake just fine. WinRAR Moving on to compression tests, we used WinRAR’s built-in benchmark to measure the compression performance of the various chips. We no longer break out the performance of the Ryzen 5 1600X and the Core i5-7600K CPUs. That’s because both of those were tested with the RAM set at DDR4/2933. Memory bandwidth doesn’t matter that much in 3D rendering tests, but it definitely can tilt the scales in compression tests. Rather than cloud the results, we’re dropping
them. One thing you’ll notice is that the 10-core Core i9 suddenly takes second place to the 10-core Core i7 processor.
We also tried this test with the latest beta version of WinRAR and saw no change. We surmised this might be the cache design of the new chip, but after talking with Intel, the company suggested it could be the new mesh design. Handbrake Our encoding test uses the free Handbrake to convert a 30GB 1080p MKV file using Handbrake 0.9.9 Android Tablet preset. The test is multithreaded and scales well with clock speed. The winner is the Core i9-7900X, which comes in about 10 percent faster than the 10-
core Core i7-6950X. We’re also seeing nice scaling: the 10-core is about 30 percent faster than the 8-core Core i7-6900K and 60 percent faster than the 6-core Core i7-6800K. 3DMark Fire Strike For gaming performance, we first run Futuremark’s 3DMark Fire Strike. We’re reporting only the physics portion of the test, as that’s the only one that matters for the CPU. The test uses a real-world physics engine that scales well with core count. Oddly, the Core i7-6950X nudges the Core i9-7900X out of the way, perhaps because of the cache difference between the chips or the mesh architecture. Note, though, that this is a theoretical test of what a game could do if it stressed all those cores. In reality, games don’t devote this much to game physics.
Tomb Raider Moving on to a real game, we use Ubisoft’s older Tomb Raider to measure CPU performance by running the game at 1920x1080 resolution and the normal preset. At this low game setting and relatively low resolution for a GeForce GTX 1080, the only difference we’re likely seeing is clock speed. Each CPU’s cache can occasionally move the needle, too.
The Ryzen 7 1800X chip performance is off, likely due to code that isn’t optimized for its micro architecture. Case in point, Rise of the Tomb Raider recently received an update that greatly helped Ryzen out. And for the most part, it’s not an issue at higher game settings where the GPU is the bottleneck on performance.
You can also see from our results why Ryzen’s performance was so confusing: CPUs don’t matter
in conventional gaming as much as people wish they would.
If you point your eyes at that last chart, which includes just about every Intel design represented since Sandy Bridge, you can only conclude that the new Core i9-7900X is the fastest consumer CPU ever produced by Intel. There’s just no argument. The fact that it’s being offered at £910 compared to the £1,600 tag on the previous 10-core part is another reason for the PC community to cheer.
The problem is, it’s a different world now. At £910 for a 10-core chip, you’re paying about 100 percent over an 8-core Ryzen 7 chip for about 30 percent more performance. Even worse, we still don’t know what price AMD set for its 12-core and 16-core Threadripper chips. If AMD introduces a 12-core CPU at £850, as some predict, a 10-core Core i9 for £910 loses its lustre. For now, the Core i9-7900X reigns as the fastest consumer CPU on the planet. But it should be looking over its shoulder, as will we, for Threadripper. Gordon Mah Ung
• 10 cores • 20 threads • 3.3GHz Processor Base Frequency • 4.3GHz Max Turbo Frequency • 13.75MB L3 cache • 8GT/s DMI3 bus speed • 4.5GHz Intel Turbo Boost Max Technology 3.0
• 140W TDP • 128GB max memory size • DDR4-2666 memory type • 4 memory channels • Intel Optane Memory Supported • Intel Turbo Boost Max Technology 3.0 • IntelTurbo Boost Technology 2.0 • Intel Hyper-Threading Technology • Intel Virtualization Technology • Intel Virtualization Technology for Directed I/O • Intel 64 • 64-bit instruction set • SSE4.1/4.2, AVX 2.0, AVX-512 • Enhanced Intel SpeedStep Technology
The Core X series is made up of CPUs constructed with Skylake-X cores and Kaby Lake-X cores. The monster 18-core part is due in October
AVX 512 in the Skylake-X promises far more performance, but only if the code supports it
Skylake is very different from Skylake-X, and much of that has to do with the cache, AVX512, and a new mesh interface