For the past eighteen months, Intel has paraded its new ‘Lakefield’ processor design around the press and the public as a paragon of new processor innovation. Inside, Intel pairs one of its fast peak performance cores with four of its lower power efficient cores, and uses novel technology in order to build the processor in the smallest footprint it can. The new Lakefield design is a sign that Intel is looking into new processor paradigms, such as hybrid processors with different types of cores, but also different stacking and packaging technologies to help drive the next wave of computing. With this article, we will tell you all you need to know about Lakefield.

Part Smartphone, Part PC

When designing a processor, there are over a thousand design choices to be made. The processor can be built to tackle everything, or it can be aimed at a niche. For high performance computing, there might be a need for a high power, high performance design where cooling is of no consideration – compare that to a processor aimed at a portable device, and it needs to be energy efficient and offer considerable battery life for a fixed battery size. There is also the cost of designing the product, how much to invest into research and development, how many units are expected to sell, and thus how many should be produced and what size the product should be. What the price range of the target market is can be a huge factor, even before putting pen to paper.


The New Samsung Galaxy Book S

This is all why we have big multi-core processors with lots of compute acceleration in servers, more moderate power and core counts in home machines that focus on single core performance and user experience, and why smartphone processors have to physically fit into a small design and offer exceptional battery life.

Laptop processors have always sort of fit into the middle of the PC and smartphone markets. Laptop users, especially professionals and gamers, need the high performance that a desktop platform can provide, but road warriors need something that is superbly efficient in power consumption, especially at idle, to provide all-day battery life as if they were on a good smartphone. Not only this, but the more energy efficient and the smaller the footprint of the processor and its features, the thinner and lighter the laptop can be, offering a premium design experience.

As a result, we have seen the ultra-premium notebook market converge from two directions.

From the top, we have AMD and Intel, using their laptop processor designs in smaller and smaller power envelopes to offer thin and light devices with exceptional performance and yet retain the energy efficiency required for battery life. For the most premium designs, we see 12-15+ hours of laptop battery life, as well as very capable gaming.

From the bottom, we have Qualcomm, building out its high-performance smartphone processor line into larger power envelopes, in order to offer desktop-class performance with smartphone-class connectivity and battery life. With the designs using Qualcomm’s processors, a user can very easily expect 24+ hours of battery life, and with regular office use, only charge the system once every couple of days. Qualcomm still has an additional barrier in software, which it is working towards.

Both of these directions converge on something in the middle – something that can offer desktop-class performance, 24hr+ battery life, capable gaming, but also has a full range of software support. Rather continue with trying to bring its processors down to the level it requires, Intel has decided to flip its traditional processor paradigm upside down, and build a smartphone-class processor for this market, matching Qualcomm in its bottom up approach while also looking into novel manufacturing techniques in order to do so.

This processor design is called ‘Lakefield’.

Lakefield at the Core, and the Atom

For the past two decades, Intel has had two different types of x86 CPU design.

The Big ‘Core’ CPU

Intel calls its high power/high performance x86 design the ‘Core’ family. This can make it very confusing, to differentiate between the general concept of a processor core and a ‘Core’-based processor core.

Over the years, Core-based processor cores have been designed for power envelopes from low-power laptops all the way up to the beefiest of servers. The Core line of processor cores implement more complex logic in order to provide additional acceleration, at the expense of physical size and power.

The Small ‘Atom’ CPU

The second type of x86 design from Intel is its more energy efficient implementation, called ‘Atom’. With the Atom cores, Intel simplifies the design in order to maximise efficiency for a given power or a given performance. This makes the design smaller, cheaper to manufacturer, but has a lower peak performance than the Core design. We typically see Atom designs in power restricted scenarios where performance is not critical, such as IoT, or low cost laptop designs.

Where Core Meets Atom

Normally we characterise a processor core design in terms of this power and performance. Due to the variation in the design, we see where some designs work best, at various points for a given power or for a given performance. In the case of Intel’s latest generation of Core and Atom hardware, it looks something like this, if we compare one thread against one thread:


Modified from Intel’s Slides

From this graph, which measures Performance on the bottom axis and power on the side axis, there is a crossover point where each design makes the best sense. When the demand for performance is below 58%, the Atom design is the most power efficient, but above 58% then a Core design is preferred.

Homogenous CPUs (all the same) vs
Heterogeneous CPUs (mix of different)

Now in modern processors, especially in laptops, desktops, and servers, we only experience one type of core design. We either have all Core or all Atom, and the performance is designed to scale within those homogeneous designs. It becomes a simple curve to navigate, and when more parallel performance is required, more of those types of cores are fired up to serve the needs of the end user. This has been the case for these markets for the last 30-50 years.

The smartphone space, for the last decade, has been taking a different approach. Within the smartphone world, there are core designs listed as ‘big’ and core designs listed as ‘little’, in the same way that Intel has Core and Atom designs.

These smartphone processors combine numbers of big cores with numbers of small cores, such that there is an intrinsic benefit to running background tasks on the little cores, where efficiency is important, and user experience related elements on the big cores, where latency and performance is important.

The complexity of such a heterogeneous smartphone-like design has many layers. By default most items will start on the little cores, and it is up to either the processor or the operating system to identify when the higher performance mode during a user experience moment is needed. This can be tricky to identify.

Then also comes the matter when a workload has to actually move from one type of core to the other, typically in response to a request for a specific level of performance – if the cores are designed significantly different, then the demands on the memory can likely increase and it is up to the operating system to ensure everything works as it should. There is also an additional element of security, which is a larger topic outside of the scope of this article.

Ultimately building a design with both big cores and little cores comes down a lot to what we call the scheduler. This is a program inside the operating system that manages where different background processes, user experience events, or things like video editing and games, get arranged. The smartphone market has been working on different types of schedulers, and optimizing the designs, for over a decade as mentioned. For the land of Intel and AMD, the push for heterogeneous schedulers has been a slow process by comparison, and it becomes very much a chicken and egg problem – there is no need for an optimized heterogeneous scheduler if there is never a heterogeneous processor in the market.

So why bring all this up?

Lakefield is the first x86 heterogeneous processor.

In its marketing, Intel calls this a ‘hybrid’ CPU, and we will start to see logos identifying this as such. At the heart of its design, Lakefield combines one of the big Core designs with a cluster of four smaller Atom designs, all into one single piece of silicon. In normal x86 processor talk, this is essentially a ‘penta-core’ design, which will commonly be referred to as a 1+4 implementation (for one big core and four small cores).

Intel’s goal with Lakefield is to combine the benefits of the power efficient Atom core with the better user-experience elements provided by the more power hungry but better peak performing big Core. As a result, it sits in the middle of Intel’s traditional homogeneous designs which only contain one type of x86 design – somewhere above the ‘all Atom’ 0+4 design and somewhere below the ‘all Core’ 4+0 design (in actual fact, it’s closer to 0+4).

Based on our conversations with Intel, and the small demonstrations we have seen so far, the best way to consider the new Lakefield processor is to consider it similar to one of the older quad-core Atom processors, with the benefits of the single core performance of a big Core. The cluster of four smaller Atom CPUs will take care of the heavy lifting and parallel performance requests, because there are four of them, while the big Core will respond when the user loads an application, or touches the screen, or scrolls a web browser.

Being a new form of x86 hybrid CPU is not the only thing that Lakefield brings to the table.

Now, just for some form of clarification, we have already had some experience with these sorts of hybrid CPU designs on operating systems like Windows. Qualcomm’s Windows on Snapdragon laptops, like the Lenovo Yoga, use a 4+4 design with the Snapdragon smartphone chips, and Qualcomm has had to work extensively with Microsoft to develop an appropriate scheduler that can manage workloads between the different CPU designs.

The main difference to what Qualcomm has done and what Intel is doing with Lakefield is in software support – Qualcomm processors run ‘Arm’ instructions, while Intel processors run ‘x86’ instructions. Most Windows software is built for x86 instructions, which has limited Qualcomm’s effectiveness in penetrating the traditional laptop market. Qualcomm's design actually allows for ‘x86 translation’, however its scope is limited and there is a performance penalty, but is a work in progress. The point being is that while we have not had a hybrid CPU scheduler for Windows on an x86 system previously, there has been a lot of work put in by Microsoft to date while working with Qualcomm.

Visualising Heterogeneous CPU Designs


Not to any sort of scale

Here are some examples of mobile processors, from Intel and Qualcomm, with the cores in green. On the left is Intel's own Ice Lake processor, with four big cores. In the middle is Intel's Lakefield, which has two stacked silicon dies, but it's the top one that has one big core and four small ones. On the right is Qualcomm's Snapdragon 8cx, currently used in Windows on Snapdragon devices, which uses four performance cores and four efficiency cores, but also integrates a smartphone modem onboard.

In this article, over the following pages, we'll be looking at Intel's new Lakefield processor in detail, covering the new multi-core design, discussing chiplets and Intel's new die-to-die bonding technology called Foveros, the implications of such a design on laptop size (as well as looking at the publicly disclosed Lakefield laptops coming to market), die shots, supposed performance numbers, thermal innovations, and the future for Lakefield. Data for this article has come from our research as well as interviews with Intel's technical personnel and Intel's own presentations on Lakefield at events such as HotChips, Architecture Day, CESIEDM, and ISSCC. Some information is dissected with helpful input from David Schor of Wikichip. We also cover some of Intel’s innovations with the scope of other semiconductor companies, some of which may be competitors.

A Stacked CPU: Intel’s Foveros
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  • justing6 - Thursday, July 2, 2020 - link

    Amazing article! I learned so much about Lakefield and 3D stacking in general. The technology and engineering is really incredible, but as a consumer product it looks extremely lacking.

    I'm a proud owner and heavy user of a Surface Pro X, and the 8cx/SQ1 is generally "good enough" when running ARM workloads. Going to a 15W Intel chip that can turbo to 25-40W feels noticeably snappier, but when considering the SQ1 is 7W-15W it's really impressive. The 4+4 also allows for very good multitasking performance, it takes 10GB+ of heavy web browser tabs running on an external 3440x1440p display before it really feels like it starts to slow down.

    However, that's when I live inside Chromium Edge running native ARM64 code. Performance is still laughable compared to Apple Silicon, especially for translated x86 code. On Geekbench the A12z on the dev kits running translated x86 code is just as fast as the 8cx running native ARM code, while the 8cx's performance really suffers when it has to run anything more complicated than a text editor or video player written in x86. I expect Apple's successor to the A12z to mop the floor with this whole market at the same price points, even for x86 code. On top of this, Apple has unparalleled leverage over developers by controlling its entire hardware stack. I wouldn't be surprised if in 2 years, all major MacOS applications will be compiled for native ARM64 code. On the other hand, Windows on ARM64 is almost 2 years old now and has very few natively compiled apps.

    I really prefer Windows, but it's going to be a hard choice for me and a lot of consumers if a Lakefield/8cx ultraportable running Windows costs the same as an Apple ultraportable on Silicon that has somewhere around double the performance for the same price, while still keeping a thin and light design with great battery life. Intel and Qualcomm will be fighting for a distant second place.
    Reply
  • jeremyshaw - Thursday, July 2, 2020 - link

    So you're saying a desktop with desktop TDP outperforms a fanless tablet with tablet TDP?

    I do agree Apple has a stronger push (and will have to, since they are moving their entire ecosystem over, and anyone that isn't fully onboard will simply be left behind).

    Qualcomm got too greedy, Nvidia doesn't want to fight in that market anymore (remember the original Surface tablets with Nvidia Tegra chips?), and nobody else is really eyeing the laptop/consumer segment outside of Apple.

    Oh, well. Some people are propping up the PINE64 as if it's worth anything.
    Reply
  • lmcd - Thursday, July 2, 2020 - link

    No one's come up with an exciting killer app beyond video decoding for smartphones or tablets so might as well "prop up" the PINE64 :)

    Hopefully Broadcom will get interested in SoCs again with the work they're doing with the RPi foundation. ARM is going toward powerful CPU cores anyway so it shouldn't take an Apple-sized company to come up with competitive ARM designs.
    Reply
  • justing6 - Thursday, July 2, 2020 - link

    Considering an iPad Pro (a fanless tablet) running an A12z puts up Geekbench 5 scores 30% to 60% higher that the SQ1/8cx single/multi core respectively when running native ARM code, it's safe to say its a generation or two ahead of anything Qualcomm has. I also doubt they changed much with the TDP of the chip in the Arm transition Dev kit, if anything they made it less powerful by disabling the 4 small cores and leaving it only with the 4 large cores to give them more time to work out the big.LITTLE scheduling in MacOS. A 30% hit to performance when running x86 code sounds about right, its just that the chip has so much more raw power than the 8cx that it will be able to give users a much better experience.

    I'm not an Apple fan by any means, but I am a fan of innovation. Apple has been pretty stagnant on that front the past decade, but with the move to ARM they have a chance to really get ahead of the market like the Apple of the 2000s.
    Reply
  • serendip - Thursday, July 2, 2020 - link

    The ARM MacOS devices could be mobile powerhouses at (gasp!) equal price points as Windows devices running either ARM or x86. Imagine a $1000 Macbook A13 or A14 with double the performance than a Surface Pro X or Galaxy Book S costing the same. Reply
  • lmcd - Friday, July 3, 2020 - link

    Considering the hurdles just to use any form of open source software with the platform, they're not equal. Reply
  • JayNor - Thursday, July 2, 2020 - link

    Intel already makes LTE modems. By chiplet, I am referring to the Foveros 3D stackable chiplets in this case ... Intel also makes emib stitched chiplet form features for their FPGAs. So, not just a marketing term. These have to implement certain bus interfaces or TSV placement requirements to work with the FPGA or Foveros manufacturing. Reply
  • henryiv - Thursday, July 2, 2020 - link

    What a shame to disable AVX-512. The circuitry is probably left there to support SSE, which is still a common denominator with Tremont cores. Also, 5 cores not running together is a huge huge bummer.

    This first generation is an experimental product and is to be avoided. In the next generation, the Tremont successor will probably get at least 256-bit AVX support, which will be finally possible to use across 5 cores. Transition to 7nm should also give the elbow room needed to run all 5 cores at the same time at full throttle within the limited 7w power budget.
    Reply
  • jeremyshaw - Thursday, July 2, 2020 - link

    By the usual Intel Atom timeline, it will be 2023 before a Tremont successor comes out. By then, will anyone even care about Intel releases anymore? Reply
  • lmcd - Thursday, July 2, 2020 - link

    Bad joke, right? Intel is signaling that Atom is moving to the center of their business model. Previous times Intel prioritized Atom, Atom got every-other-year updates. I'd expect a 2022 core or sooner, if you assume Tremont was "ready" in 2019 but had no products (given 10nm delays and priority to Ice Lake). Reply

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