Intel’s direction for the high-end desktop space has taken an interesting turn. After several years of iterative updates, slowly increasing core counts and increasing IPC, we have gotten used to being at least one generation of microarchitecture behind the mainstream consumer processor families. There are many reasons for this, including enterprise requirements for long support platforms as well as enterprise update cycles. For 2017, Intel is steering the ship in a slightly different direction, and launching the latest microarchitecture on the HEDT platform. These CPUs don’t feature the high core counts of the other HEDT parts, but offer a higher point up the voltage/frequency scale to be the fastest single thread processors money can buy. They also overclock quite well.

The High-Level Product

Back at Computex, Intel announced its new high-end desktop (HEDT) platform code named Basin Falls. There are three elements to Basin Falls: the new X299 chipset which brings a number of enhancements from the more mainstream consumer line, a set of Skylake-X processors based on the Skylake-SP microarchitecture (and slightly different from the mainstream Skylake-S processors launched in 2015) from 6 cores to 18 cores, and a pair of Kaby Lake-X processors, reusing the Kaby Lake-S silicon launched earlier this year but with a bit more frequency and power consumption.

We covered all three parts in our launch pieces (linked below), but here is a quick recap.

Pushing Peak Performance

The main reasons an enthusiast invests in the HEDT platform usually revolve around multi-threaded performance, the need to support multiple graphics cards, and potentially 1.21 jiggabytes of DRAM (ed: you mean 128GB). Kaby Lake-X (KBL-X for short) doesn’t have any of these features that we normally prescribe to HEDT: it only has four cores, not ten or higher; it only supports one GPU at full PCIe speed, up to two in SLI or three in Crossfire if you are willing to have a lower link speed; and it only has dual channel memory for a maximum of 64GB. So why is Intel bringing KBL-X to HEDT? The answer lies primarily in peak performance.

Users that have been in the enthusiast space will have realized that the Holy Grail for PC performance is single threaded (ST) performance. If you master single thread throughput, then arguably the rest is easier, such as scaling out to more cores. There are usually three barriers to high ST-perf: instructions per clock (IPC), frequency and power consumption. A high IPC is fundamental to such a design, as any gains will propagate through the platform, but is becoming a tough job. Over the last few generations, Intel has increased IPC by 3-10% each generation, making a 30-45% increase since 2010 and Sandy Bridge depending on the benchmark, but we’re unlikely to see 50-100% jumps per generation any time soon. Any IPC gains are multiplied through the frequency at which the processor runs at, which can be limited by a combination of things: production process (e.g 14nm), voltage characteristics, stability, yield etc. These features tie directly into power consumption, which increases as a square of voltage and with frequency/capacitance. With some designs, +10% frequency might be possible, but at the cost of +100% power, so there also needs to be a balance to have something marketable that people will want to buy.

Kaby Lake-X is binding Intel’s latest x86 microarchitecture with the highest IPC, at the highest frequency they have ever launched a consumer CPU, for a reasonable power window. Users can overclock another 10% fairly easily, for a slight increase in power. Simply put, Kaby Lake-X is the highest single-thread performing x86 processor out-of-the-box that exists. This is a different take on HEDT compared to previous generations of HEDT CPUs.

With the extra single thread performance, it would appear to appeal to traders who need fast systems, gamers where single thread performance is limiting the frame rate (or minimum frame rates), or science/enterprise workloads where serial code is a limiting factor for simulations or professional applications.

The Core i7 and the Core i5

At the heart, the new KBL-X processors are no different to their mainstream platform KBL-S brethren. The silicon is the same, but potentially binned for a better voltage/frequency curve, and then packaged into the HEDT platform rather than the mainstream platform. Unlike the mainstream processor stack though, Intel is only launching two processors. A Core i7-7740X and a Core i5-7640X.

Intel Kaby Lake Processors
  Core i7 Core i5
Core i7-7740X Core i7-7700K Core i5-7640X Core i5-7600K
Socket LGA2066 LGA1151 LGA2066 LGA1151
Cores/Threads 4/8 4/8 4/4 4/4
Base Frequency 4.3 GHz 4.2 GHz 4.0 GHz 3.8 GHz
Turbo Frequency 4.5 GHz 4.5 GHz 4.2 GHz 4.2 GHz
TDP 112 W 91 W 112 W 91 W
L2 Cache 256 KB/core
L3 Cache 8 MB 6 MB
DRAM Channels 2
DRAM Support DDR4-2666 DDR4-2400 DDR4-2666 DDR4-2400
Graphics None HD 620 None HD 620
Price (MSRP) $350 $250
Price (7/21) $349 $309 $248 $239
Launched July 2017 Jan 2017 July 2017 Jan 2017

Both CPUs are quad core, with the Core i7 having Hyperthreading for a total of eight threads. The Core i5 does not have hyperthreading, making it the first HEDT processor in the modern Core era to do so. Both will have identical support to their KBL-S siblings, although the increased base/turbo frequencies have resulted in Intel’s TDP increasing from 95W to 112W. The TDP rating is a guide for appropriate cooling: the KBL-S processors were actually very good on their power consumption at stock frequencies, and as shown later, so are the KBL-X processors. Intel could have kept the 95W TDP rating very easily here.

So given what was said in the previous section about peak performance, the Core i7 fits the bill. It has the highest frequencies, and supports hyperthreading for increased performance. It begs the question why the Core i5 exists at all. There are a few guesses as to why:

  • For some enterprise users, hyperthreading is not needed
  • It is a cheaper entry point into the platform
  • It overclocks just as well to perform the same as the Core i7

Intel’s official line is about giving customers options. We will not be seeing a Core i3 on HEDT any time soon, though.

Kaby Lake-X does not come with any bundled cooler, but Intel is promoting its own TS13X liquid cooled loop with the processors. This CLC has been in the market for a good number of years now.

Competition and Market

Because these new KBL-X parts are updates to the KBL-S family, Intel has direct competition with itself. The Core i7-7740X is an alternative to the Core i7-7700K on the mainstream platform, being similar in frequency but giving much higher platform costs.

Comparison: Intel Core i7-7740X vs Core i7-7700K
Core i7-7740X
Features Intel
Core i7-7700K
X299 Platform Z270 etc
LGA2066 Socket LGA1151
4 / 8 Cores/Threads 4 / 8
4.3 / 4.5 GHz Base/Turbo 4.2 / 4.5 GHz
16 PCIe 3.0 Lanes 16
256 KB/core L2 Cache 256 KB/core
8 MB L3 Cache 8 MB
112W TDP 95W
$349 Retail Price (7/21) $309
MSI X299 Raider: $230
ASUS Prime X299-A: $310
GIGABYTE X299-UD4: $249
Cheap OC
GIGABYTE Z270-HD3: $114
MSI Z270 SLI PLUS: $136
ASUS TUF Z270-MK2: $120

Similar platform builds for the two put an extra $100-150 cost on the motherboard, potentially limiting the usefulness of the new KBL-X parts on paper, as that extra cost of the build as a whole might not warrant another 100 MHz on the turbo frequency. The proof is in the pudding, which is why we are doing this review. The Core i5-7640X against the Core i5-7600K is in a similar situation.

However, there is also AMD to discuss. With the launch of the Ryzen family of processors, There are now significant comparisons to be made between what Intel offers and what AMD offers. Going at a price-for-price comparison, using MSRP prices (not sale prices or distributor prices), the Core i7-7740X squares against AMD’s Ryzen 7 1700.

Comparison: Intel Core i7-7740X vs AMD Ryzen 7 1700
Core i7-7740X
Features AMD
Ryzen 7 1700
X299 Platform X370, B350, A320
LGA2066 Socket AM4
4 / 8 Cores/Threads 8 / 16
4.3 / 4.5 GHz Base/Turbo 3.0 / 3.7 GHz
16 PCIe 3.0 Lanes 16
256 KB/core L2 Cache 512 KB/core
8 MB L3 Cache 16 MB (Victim Cache)
112W TDP 65W
$349 Retail Price (7/21) $270
MSI X299 Raider: $230
ASUS Prime X299-A: $310
GIGABYTE X299-UD4: $249
Cheap OC
ASUS Prime B350-Plus: $90
MSI B350 Tomahawk: $100
ASRock AB350 Pro4: $100

At this price, both sides have their merits. Intel wins in IPC, which is about 5-15% ahead clock-for-clock, but is also at a higher frequency compounding the difference. In its own attack, AMD wins in cores and threads, offering eight cores and sixteen threads where Intel only offers four cores and eight threads. Intel wins for the IO and chipset, offering 24 PCIe 3.0 lanes for USB 3.1/SATA/Ethernet/storage, while AMD is limited on that front, having 8 PCIe 2.0 from the chipset. Depending on the workload, both sides have merits – AMD will state that it is geared towards more professional multi-threaded workloads, while Intel is geared towards serial code scenarios which still dominate certain tasks. There’s also the platform cost, where the motherboards are $150-$200 cheaper for AMD when looking at cheap overclockable systems.

For the Core i5-7640X, it sits at a similar price to AMD’s Ryzen 5 1600X.

Comparison: Intel Core i5-7640X vs AMD Ryzen 5 1600X
Core i5-7640X
Features AMD
Ryzen 5 1600X
X299 Platform X370, B350, A320
LGA2066 Socket AM4
4 / 4 Cores/Threads 6 / 12
4.2 / 4.4 GHz Base/Turbo 3.6 / 4.0 GHz
16 PCIe 3.0 Lanes 16
256 KB/core L2 Cache 512 KB/core
8 MB L3 Cache 16 MB (Victim Cache)
112W TDP 95W
$248 Retail Price (7/21) $230
MSI X299 Raider: $230
ASUS Prime X299-A: $310
GIGABYTE X299-UD4: $249
Cheap OC
ASUS Prime B350-Plus: $90
MSI B350 Tomahawk: $100
ASRock AB350 Pro4: $100

For this review, we have also included numbers for other processors. These include AMD’s Ryzen 7 1800X, which at $499 is an alternative due to the money saved by investing on the AM4 platform; we also have the Skylake-X based Core i7-7800X, which has an MSRP not so far away from the i7-7740X, and opens up the platform with more PCIe lanes, two more cores, but at the expense of single thread performance; and finally the perennial Core i7-2600K from the Sandy Bridge era, for the benchmarks which we have data.

Given everything said above, it would appear Intel has an uphill struggle to convince users that Kaby Lake-X is worth the investment. In this review we will test and see what the performance story is.

Please note that our AMD data is before AGESA We are planning an article with an update of the latest AGESA soon.

Pages In This Review

Navigating the X299 Minefield: Kaby Lake-X Support
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  • Santoval - Tuesday, July 25, 2017 - link

    That is not how IPC works, since it explicitly refers to single core - single thread performance. As the number of cores rises the performance of a *single* task never scales linearly because there is always some single thread code involved (Amdahl's law). For example if your task has 90% parallel and 10% serial code its performance will max out at x10 that of a single core at ~512 cores. From then on even if you had a CPU with infinite cores you couldn't extract half an ounce of additional performance. If your code was 95% parallel the performance of your task would plateau at x20. For that though you would need ~2048 cores. And so on.

    Of course Amdahl's law does not provide a complete picture. It assumes, for example, that your task and its code will remain fixed no matter how many cores you add on them. And it disregards the possibility of computing distinct tasks in parallel on separate cores. That's where Gustafson's Law comes in. This "law" is not concerned with speeding up the performance of tasks but computing larger and more complex tasks at the same amount of time.

    An example given in Wikipedia involves boot times : Amdahl's law states that you can speed up the boot process, assuming it can be made largely parallel, up to a certain number of cores. Beyond that -when you become limited by the serial code of your bootloader- adding more cores does not help. Gustafson's law, on the contrary, states that instead of speeding up the boot process by adding more cores and computing resources, you could add colorful GUIs, increase the resolution etc, while keeping the boot time largely the same. This idea could be applied to many -but not all- computing tasks, for example ray tracing (for more photorealistic renderings) and video encoding (for smaller files or videos with better quality), and many other heavily multi-threaded tasks.
  • Rickyxds - Monday, July 24, 2017 - link

    I just agree XD.
  • Diji1 - Wednesday, July 26, 2017 - link

    "Overall speed increase 240%."

    LMAO. Ridiculous.
  • Alistair - Wednesday, July 26, 2017 - link

    No reason to laugh. I compared the 6600k vs the Ryzen 1700. 1 year speed increase of 144 percent (2.44 times the speed). Same as this: 1135 vs 466 points.
  • Dr. Swag - Tuesday, July 25, 2017 - link

    I disagree, best value is 1600 as it oces as well as 1600x, comes with a decent stock cooler, and is cheaper.
  • vext - Monday, July 24, 2017 - link

    Interesting article but it seems intended to play down the extremely bad press x299 has received which is all over the internet and Youtube.

    Once you get past Mr. Cuttress' glowing review, it's clear that the I5-7640x is not worth the money because of lackluster performance, the I7-7740X is marginally faster than the older 7700k, and the I7-7800x is regularly beaten by the 7740X in many benchmarks that actually count and is a monstrously inefficient energy pig. Therefore the only Intel CPUs of this batch worth buying are the 7700k/7740x, and there is no real advantage to x299. In summary, it doesn't actually change anything.

    It's very telling that Mr. Cutress doesn't comment on the absolutely egregious energy consumption of the 7800x. The Test Bed setup section doesn't list the 7800x at all. The 7840x and 7740x are using a Thermalright True Copper (great choice!) but no info on the 7800x cooler. Essentially, the 7800x cameo appearance is only to challenge the extremely strong Ryzen multi-threaded results, but its negative aspects are not discussed, perhaps because it might frighten people from x299. Tsk, tsk. As my 11 year old daughter would say "No Fair." By the way, the 7800x is selling for ~ $1060 right now on Newegg, not $389.

    Proudly typed on my Ryzen 1800x/Gigabyte AB350 Gaming 3. # ;-)
  • Ian Cutress - Monday, July 24, 2017 - link

    You may not have realised but this is the Kaby Lake-X review, so it focuses on the KBL-X parts. We already have a Skylake-X review for you to mull over. There are links on the first page.
  • mapesdhs - Monday, July 24, 2017 - link

    Nevertheless, the wider picture is relevant here. The X299 platform is a mess. Intel is aiming KL-X at a market which doesn't exist, they've locked out features that actually make it useful, it's more power hungry, and a consumer needs a lot of patience and plenty of coffee to work out what the heck works and what doesn't on a mbd with a KL-X fitted.

    This is *exactly* the sort of criticism of Intel which should have been much stronger in the tech journalism space when Intel started pulling these sorts of stunts back with the core-crippled 3930K, heat-crazy IB and PCIe-crippled 5820K. Instead, except for a few exceptions, the tech world has been way too forgiving of Intel's treading-on-water attitude ever since SB, and now they've panicked in response to Ryzen and released a total hodgebodge of a chipset and CPU lineup which makes no sense at all. And if you get any disagreement about what I've said by anyone at Intel, just wave a 4820K in their face and say well explain this then (quad-core chip with 40 PCIe lanes, da daa!).

    I've been a big fan of Z68 and X79, but nothing about Intel's current lineup appeals in the slightest.
  • serendip - Tuesday, July 25, 2017 - link

    There's also the funny bit about motherboards potentially killing KBL-X CPUs if a Skylake-X was used previously.

    What's with Intel's insane product segmentation strategy with all the crippling and inconsistent motherboard choices? It's like they want to make it hard to choose, so buyers either get the cheapest or most expensive chip.
  • Haawser - Tuesday, July 25, 2017 - link

    'EmergencyLake-X' is just generally embarrassing. Intel should just find a nearby landfill site and quietly bury it.

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