Architectural Background

Intel is ready with the Kaby Lake-S processor family for consumers. Our review of the 7700K follows.

It probably doesn't surprise any of our readers that there has been a tepid response to the leaks and reviews that have come out about the new Core i7-7700K CPU ahead of the scheduled launch of Kaby Lake-S from Intel. Replacing the Skylake-based 6700K part as the new "flagship" consumer enthusiast CPU, the 7700K has quite a bit stacked against it. We know that Kaby Lake is the first in the new sequence of tick-tock-optimize, and thus there are few architectural changes to any portion of the chip. However, that does not mean that the 7700K and Kaby Lake in general don't offer new capabilities (HEVC) or performance (clock speed). 

The Core i7-7700K is in an interesting spot as well with regard to motherboards and platforms. Nearly all motherboards that run the Z170 chipset will be able to run the new Kaby Lake parts without requiring an upgrade to the newly released Z270 chipset. However, the likelihood that any user on a Z170 platform today using a Skylake processor will feel the NEED to upgrade to Kaby Lake is minimal, to say the least. The Z270 chipset only offers a couple of new features compared to last generation, so the upgrade path is again somewhat limited in excitement.

Let's start by taking a look at the Core i7-7700K and how it compares to the previous top-end parts from the consumer processor line and then touch on the changes that Kaby Lake brings to the table.

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With the beginning of CES just days away (as I write this), Intel is taking the wrapping paper off of its first gift of 2017 to the industry. As you can see from the slide above, more than just the Kaby Lake-S consumer socketed processors are launching today, but other components including Iris Plus graphics implementations and quad-core notebook implementations will need to wait for another day.

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For DIY builders and OEMs, Kaby Lake-S, now known as the 7th Generation Core Processor family, offer some changes and additions. First, we will get a dual-core HyperThreaded processor with an unlocked designation in the Core i3-7350K. Other than the aforementioned Z270 chipset, Kaby Lake will be the first platform compatible with Intel Optane memory. (To be extra clear, I was told that previous processors will NOT be able to utilize Optane in its M.2 form factor.)

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Though we have already witnessed Lenovo announcing products using Optane, this is the first official Intel discussion about it. Optane memory will be available in M.2 modules that can be installed on Z270 motherboards, improving snappiness and responsiveness. It seems this will be launched later in the quarter as we don't have any performance numbers or benchmarks to point to demonstrating the advantages that Intel touts. I know both Allyn and I are very excited to see how this differs from previous Intel caching technologies.

  Core i7-7700K Core i7-6700K Core i7-5775C Core i7-4790K Core i7-4770K Core i7-3770K
Architecture Kaby Lake Skylake Broadwell Haswell Haswell Ivy Bridge
Process Tech 14nm+ 14nm 14nm 22nm 22nm 22nm
Socket LGA 1151 LGA 1151 LGA 1150 LGA 1150 LGA 1150 LGA 1155
Cores/Threads 4/8 4/8 4/8 4/8 4/8 4/8
Base Clock 4.2 GHz 4.0 GHz 3.3 GHz 4.0 GHz 3.5 GHz 3.5 GHz
Max Turbo Clock 4.5 GHz 4.2 GHz 3.7 GHz 4.4 GHz 3.9 GHz 3.9 GHz
Memory Tech DDR4 DDR4 DDR3 DDR3 DDR3 DDR3
Memory Speeds Up to 2400 MHz Up to 2133 MHz Up to 1600 MHz Up to 1600 MHz Up to 1600 MHz Up to 1600 MHz
Cache (L4 Cache) 8MB 8MB 6MB (128MB) 8MB 8MB 8MB
System Bus DMI3 – 8.0 GT/s DMI3 – 8.0 GT/s DMI2 – 6.4 GT/s DMI2 – 5.0 GT/s DMI2 – 5.0 GT/s DMI2 – 5.0 GT/s
Graphics HD Graphics 630 HD Graphics 530 Iris Pro 6200 HD Graphics  4600 HD Graphics 4600 HD Graphics  4000
Max Graphics Clock 1.15 GHz 1.15 GHz 1.15 GHz 1.25 GHz 1.25 GHz 1.15 GHz
TDP 91W 91W 65W 88W 84W 77W
MSRP $339 $339 $366 $339 $339 $332

So let's get into the details. The Core i7-7700K has a base clock of 4.2 GHz and a Turbo clock rate of 4.5 GHz for a single core. Thanks to the improved 14nm+ process technology that Intel continued to develop, Kaby Lake will see better overall clock speeds in both mobile and consumer desktop integration, giving us the performance advantages we'll see on the following pages even though we know not to expect changes on the IPC side. 

Default DDR4 frequency jumps from 2133 MHz to 2400 MHz and the integrated graphics gets a jump from HD 530 to HD 630 branding, but otherwise, that's pretty much all she wrote. The launch price will be the same as previous years – $339 for the Core i7-7700K. That's expected and reasonable considering the continued lack of competition from AMD.

How do the important consumer processors in the Kaby Lake family compare?

  Core i7-7700K Core i5-7600K Core i7-7700 Core i5-7600 Core i5-7500 Core i3-7350K
Architecture Kaby Lake Kaby Lake Kaby Lake Kaby Lake Kaby Lake Kaby Lake
Process Tech 14nm+ 14nm+ 14nm+ 14nm+ 14nm+ 14nm+
Socket LGA 1151 LGA 1151 LGA 1151 LGA 1151 LGA 1151 LGA 1151
Cores/Threads 4/8 4/4 4/8 4/4 4/4 2/4
Base Clock 4.2 GHz 3.8 GHz 3.6 GHz 3.5 GHz 3.4 GHz 4.2 GHz
Max Turbo Clock 4.5 GHz 4.2 GHz 4.2 GHz 4.1 GHz 3.8 GHz N/A
Memory Tech DDR4 DDR4 DDR4 DDR4 DDR4 DDR4
Memory Speeds Up to 2400 MHz Up to 2400 MHz Up to 2400 MHz Up to 2400 MHz Up to 2400 MHz Up to 2400 MHz
Cache (L4 Cache) 8MB 6MB 8MB 6M 6M 4M
System Bus DMI3 – 8.0 GT/s DMI3 – 8.0 GT/s DMI3 – 8.0 GT/s DMI3 – 8.0 GT/s DMI3 – 8.0 GT/s DMI3 – 8.0 GT/s
Graphics HD Graphics 630 HD Graphics 630 HD Graphics 630 HD Graphics 630 HD Graphics 630 HD Graphics 630
Max Graphics Clock 1.15 GHz 1.15 GHz 1.15 GHz 1.15 GHz 1.15 GHz 1.15 GHz
TDP 91W 91W 65W 65W 65W 60W
MSRP $339 $242 $303 $213 $192 $168

The 7700K is the highest stock clocked processor of the bunch by 300 MHz at the Turbo clock level. In a similar pattern to previous generations, the 7600K offers a quad-core option without HyperThreading at slightly reduced clock rates but for ~$100 lower price tag. The Core i7-7700 (without the K) is a non-unlocked processor but runs at noticeably lower clock speeds as well – so why it shares the same name is confusing. (Same with the Core i5-7600.) 

Though the two K-series parts have 91-watt TDPs, the other options are at 65 watts or less, even when we are matching core count and HyperThreading enablement. 

Perhaps the most interesting new part is the Core i3-7350K, an unlocked processor that offers a dual-core + HyperThreading configuration for the first time. Intel has previously released parts like the Pentium Anniversary Edition but that was limited to two threads. With a 4.2 GHz base clock it should be a damn fast part with a modest $168 price tag. It would shock me if this doesn't become one of the budget segments new darling parts.

Kaby Lake Architecture Overview

Before we get into the systems and to our results, I think it’s worth taking some time to quickly go over some of what we know about Kaby Lake from the processor perspective. Most of this content was published back in August just after the Intel Developer Forum, so if you are sure you are caught up, you can jump right along to a pictorial look at the two notebooks being tested today.

At its core, the microarchitecture of Kaby Lake is identical to that of Skylake. Instructions per clock (IPC) remain the same with the exception of dedicated hardware changes in the media engine, so you should not expect any performance differences with Kaby Lake except with improved clock speeds.

Also worth noting is that Intel is still building Kaby Lake on 14nm process technology, the same used on Skylake. The term “same” will be debated as well as Intel claims that improvements made in the process technology over the last 24 months have allowed them to expand clock speeds and improve on efficiency.

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Dubbing this new revision of the process as “14nm+”, Intel tells me that they have improved the fin profile for the 3D transistors as well as channel strain while more tightly integrating the design process with manufacturing. The result is a 12% increase in process performance; that is a sizeable gain in a fairly tight time frame even for Intel.

That process improvement directly results in higher clock speeds for Kaby Lake when compared to Skylake when running at the same target TDPs. In general, we are looking at 300-400 MHz higher peak clock speeds in Turbo Boost situations when compared to similar TDP products in the 6th generation. Sustained clocks will very likely remain voltage / thermally limited but the ability spike up to higher clocks for even short bursts can improve performance and responsiveness of Kaby Lake when compared to Skylake.

Along with higher fixed clock speeds for Kaby Lake processors, tweaks to Speed Shift will allow these processors to get to peak clock speeds more quickly than previous designs. I extensively tested Speed Shift when the feature was first enabled in Windows 10 and found that the improvement in user experience was striking. Though the move from Skylake to Kaby Lake won’t be as big of a change, Intel was able to improve the behavior.

The graphics architecture and EU (execution unit) layout remains the same from Skylake, but Intel was able to integrate a new video decode unit to improve power efficiency. That new engine can work in parallel with the EUs to improve performance throughput as well, but obviously at the expensive of some power efficiency.

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Specific additions to the codec lineup include decode support for 10-bit HEVC and 8/10-bit VP9 as well as encode support for 10-bit HEVC and 9-bit VP9. The video engine adds HDR support with tone mapping though it does require EU utilization. Wide Color Gamut (Rec. 2020) is prepped and ready to go according to Intel for when that standard starts rolling out to displays.

Performance levels for these new HEVC encode/decode blocks is set to allow for 4K 120mbps real-time on both the Y-series (4.5 watt) and U-series (15 watt) processors.

It’s obvious that the changes to Kaby Lake from Skylake are subtle and even I found myself overlooking the benefits that it might offer. 

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