Intel Core i9-7900X review: The fastest chip in the world, but too darn expensive

Intel's latest 10-core, high-end desktop (HEDT) chip—the Core i9-7900X—costs £900/$1000. That's £500/$500 less than its predecessor, the i7-6950X. In previous years, such cost-cutting would have been regarded as generous. You might, at a stretch, even call it good value. But that was at a time when Intel's monopoly on the CPU market was as its strongest, before a resurgent AMD lay waste to the idea that a chip with more than four cores be reserved for those with the fattest wallets.

The i9-7900X—which debuts the "i9" moniker alongside the new X299 platform, replacing X99—is the most powerful consumer desktop chip money can buy. In nearly every benchmark, it delivers the highest scores. In multitasking and heavily multithreaded applications like photo editors, video editors, and 3D computer graphics, it ably demonstrates the appeal of more cores. But as a product, a piece of aspirational tech to flaunt on Reddit, Intel's HEDT chips are far less alluring.

It doesn't help that X299 is a confusing mess of chips, PCIe lanes, and consumer-unfriendly feature lockouts that hint at a rushed launch in the wake of increased competition from AMD. Nor does it help that, like Intel's mainstream Kaby Lake architecture before it, Skylake-X offers little in the way of raw instructions-per-clock (IPC) performance improvement over Broadwell-E.

AMD's Ryzen is far from perfect. But when you can buy eight cores that serve even the heaviest of multitaskers and content creators for well under half the price of an Intel HEDT chip, i9 and X299 are a hard sell (except, perhaps, to fussy gamers that demand a no-compromises system).

The question is: Are you willing to pay a premium for the best performing silicon on the market? Or is Ryzen, gaming foibles and all, good enough?

When is HEDT not HEDT?

Intel's strategy for X299 is what you might call "confused," but what I'd more accurately call a clusterf**k. Where there were two tiers of HEDT chips in the past—"K" and "X" variants of a Core i7 based on the same architecture—there are now three tiers: i5, i7, and i9, all with same "X" designation. That means, for the first time in a long time, Intel's enthusiast platform supports quad-core processors. The i5-7640X offers four cores at 4.0GHz, while the i7-7740X offers four cores at 4.3GHz with hyperthreading.

The idea, according to Intel, is to give customers without the means to buy more expensive 8-core or 10-core chips a more reasonable entry point into X299 with a clear upgrade path. Except, instead of offering the full features of the X299 chipset to i5X and i7X owners—thus somewhat justifying the price premium over the mainstream chips—Intel has simply transplanted its existing i5-7600K and i7-7700K Kaby Lake processors onto the new LGA 2066 socket.

Specs at a glance	Intel Core i9-7980XE	Intel Core i9-7960X	Intel Core i9-7940X	Intel Core i9-7920X	Intel Core i9-7900X	Intel Core i7-7820X	Intel Core i7-7800X	Intel Core i7-7740X	Intel Core i5-7640X
Architecture	Skylake-X	Skylake-X	Skylake-X	Skylake-X	Skylake-X	Skylake-X	Skylake-X	Kaby Lake-X	Kaby Lake-X
Cores/Threads	18/36	16/32	14/28	12/24	10/20	8/16	6/12	4/8	4/4
Base Clock	TBC	TBC	TBC	TBC	3.3GHz	3.6GHz	3.5GHz	4.3GHz	4.0GHz
Turbo Boost 2.0	TBC	TBC	TBC	TBC	4.3GHz	4.3GHz	4.0GHz	4.5GHz	4.2GHz
Turbo Boost 3.0	TBC	TBC	TBC	TBC	4.5GHz	4.5GHz	N/A	N/A	N/A
L3 Cache	TBC	TBC	TBC	TBC	13.75MB	11MB	8.25MB	8MB	6MB
PCIe Lanes	TBC	TBC	TBC	TBC	44	28	28	16	16
Memory Support	TBC	TBC	TBC	TBC	Quad Channel DDR4-2666	Quad Channel DDR4-2666	Quad Channel DDR4-2666	Dual Channel DDR4-2666	Dual Channel DDR4-2666
TDP	TBC	TBC	TBC	TBC	140W	140W	140W	112W	112W
US Price	$2000	$1700	$1400	$1200	$1000	$599	$389	$339	$242
UK Price	~£1800	~£1600	~£1300	~£1100	£900	£550	£360	£315	£240

Neither chip supports quad-channel memory. Both come equipped with the same miserly 16 PCIe lanes, limiting compatibility with many features of X299 motherboards. A fancy board might feature three x16 PCIe slots, space for multiple M.2 SSDs, and a swathe of IO. But with a quad-core Kaby Lake-X chip installed, a lot of it won't work. To add insult to injury, Intel has removed the integrated GPU present in the i5-7600K and i7-7700K and upped the TDP to 112W.

This should result in better overclocking—and there is some evidence of that in extreme cases—but it's hard to see the value for consumers. In real-world use with practical cooling, Kaby Lake and Kaby Lake-X can be overclocked to similar speeds. The integrated GPU, while not particularly useful for high-end gaming, is great for video encoding and decoding using Intel's Quick Sync technology. That's not to mention that Z270 motherboards are much cheaper than their X299 counterparts.

Unfortunately, there are further complications up the product stack. The six-core i7-7800X and eight-core i7-7820X—which are based on Intel's older Skylake architecture—both support quad-channel memory, but only come with 28 PCIe lanes. As a point of differentiation between chips, this is nothing new. But now, with the addition of 16-lane chips, it's another point of confusion. The result of this shuffle is that X299 CPUs, at least at the lower end, are priced close to Ryzen 7 and Ryzen 5 (which feature a total of 24 PCIe lanes), albeit with fewer cores on offer.

It's not until you move up to the £900 i9-7900X that you get the full complement of 44 PCIe lanes with which to exploit the X299 platform. X299's predecessor, X99, was a forward-looking chipset, introducing features like DDR4 memory that would eventually trickle down to mainstream chips. X299 isn't quite as compelling—there's no one feature that can be lorded over Z270 users—but the number of PCIe lanes on the chipset has been bumped up from eight to 24, which are connected to the CPU via Intel's proprietary DMI connection.

The result is that X299 motherboards are blessed with a wealth of IO that includes multiple SATA ports, M.2 slots, PCIe slots, USB 3.1 ports, multiple Gigabit Ethernet ports, and in some cases Thunderbolt 3. The difficulty is finding out which ports and slots are connected directly to the CPU and which are connected via the DMI, should you care about the small latency and performance hit from the latter (most motherboard makers provide a block diagram for such matters).

On that note, Intel has introduced a new feature that ensures M.2 storage is connected directly to the CPU. Dubbed Virtual Raid On CPU, or VROC for short, the feature allows you to link several M.2 NVMe SSDs in a virtual RAID via a PCIe add-in card, running them directly to the CPU for super-fast speeds. Unfortunately, there is one rather large caveat: only RAID 0 is supported by default. For any other type of RAID array, Intel requires the purchase of a small VROC dongle, which sits in its own slot on the motherboard.

This is common practice in the enterprise world, but unheard of in consumer platforms. Consumers have a reasonable right to expect all integrated hardware features to work without the need to buy a physical key to unlock them. Pricing is yet to be confirmed, although early reports put it at between £100-£200—a significant markup over already expensive X299 motherboards.

While the i9-7900X is the most powerful chip available at launch, Intel has four more chips coming with 12, 14, 16, and 18 cores. That these chips are currently little more than a product name and a price (the 18-core i9-7980XE will cost an astonishing $2000/~£1800) is a strong indication that Intel was taken aback by AMD's Threadripper, a 16-core chip due for release this summer.

There's no word on clocks speeds, TDP, memory support, or the number of PCIe lanes for any of the top-of-the-line chips. They won't even launch until the latter half of the year.