Intel Alder Lake explained: How it enables a new generation of PCs
It's built specifically with Windows 11 in mind.
By Mark Hachman
PCWorldAug 23, 2021 9:35 am PDT
Image: Martyn Williams/IDG
Intel’s next PC microprocessor, Alder Lake, marks a radical change for Intel. Its first mainstream Core hybrid processor mixes “performance” and “efficiency” engines to deliver either performance or longer battery life when your PC needs it most.
According to Intel, Alder Lake is due “later this fall,” most likely as a 12th-gen Core chip. Intel will manufacture three versions of Alder Lake—one for the desktop, and two more for laptops—with up to 16 cores and 24 threads. Alder Lake will also mark Intel’s introduction of PCI Express 5 and DDR5 memory, executives said at its Intel Architecture Day Thursday.
Interestingly, Intel has co-designed with Microsoft a special thread scheduler, destined for Windows 11, that will optimize performance. Desktop and laptop PCs with Alder Lake inside them should mix and match higher performance where it’s needed and offer longer battery life, as Intel continues to get better at assigning the right processor core for the right task. The company says its performance core should deliver 19 percent more performance than today’s 11th-gen “Rocket Lake” desktop chip.
The bottom line? It’s probably fair to say that a major overhaul of the Intel Core PC is in the works for this fall.
What is Alder Lake?
Alder Lake, Intel’s next-gen Core architecture, will ship this fall, inside desktop and mobile PCs. Intel will offer one two-chip socketed desktop processor, plus two mobile chips: one for mainstream PCs, and one for thin-and-lights and tablets. They’re all built on Intel’s newly-renamed Intel 7 process, from 9-watt tablets to 125-watt desktops.
Alder Lake configurations will look like this, below. (Intel also uses the term “P-Cores” to describe performance cores, and “E-Cores” to describe the low-power efficiency cores.)
When Intel first disclosed Alder Lake last August, we knew then it wouldn’t be a traditional Intel processor. Inside are two types of processing cores: a “performance” core that will turn on for applications like games, and an “efficiency” core used for background tasks, like email syncing.
Arm has used this hybrid approach for many years, and the niche Intel Lakefield processor did as well. Neither excelled at performance. Raja Koduri, Intel’s senior vice president of its AXG group, sought to differentiate Alder Lake, calling it a “performance hybrid”—think Ferrari SF90 Stradale rather than Toyota Prius.
Alder Lake does not use Arm cores. Intel’s “performance” cores use Intel’s traditional “Cove” CPU design, and the efficiency cores use Intel’s Atom design.
Intel Architecture Day was for chip nerds. We’d expect Intel Innovation, a show Intel will hold on October 27 as a replacement for the venerable Intel Developer Forum, to answer the questions that chip buyers will want answered: how fast Alder Lake will run, the branding and model numbers, and how much these chips will cost.
Major changes coming with Alder Lake PCs
We already know of major changes affecting how Alder Lake PCs will be built, especially by DIY PC builders. For one, Alder Lake’s desktop processor will use an LGA1700 socket, an open secret that has surfaced as board makers and chip cooler makers design around the new chip. The larger LGA1700 socket replaces the standard LGA775 socket used for well over a decade in the PC space, which means you’ll need to buy a new motherboard and cooler if you’re building an Alder Lake PC.
Alder Lake also uses a hybrid physical memory interface that supports four different memory types: DDR4-3200, LPDDR4x-4266, and also the brand-new DDR5 technology and its DDR5-4800 and LPDDR5x modules. (DDR5, a new memory technology developed in 2017, has been in the works for years, though it’s arrived a bit later than expected.) Arik Gihon, the chief architect of Alder Lake, told attendees that Alder Lake will be able to clock the memory speed up or down, saving power, in response to real-time heuristic analysis of the work being performed. Intel’s Alder Lake will offer you the option of buying new, hotter, more expensive DDR5 memory, but you should also have the option of reusing your older PC memory.
Just as your car’s engine is really a collection of individual parts, so are Intel’s “chips” becoming a collection of individual logic blocks packaged together in various ways. Gihon referred to them as “building blocks,” and showed off some of the unexpected differences between the desktop and the mobile chips. In the diagram below, for example, you can see that the desktop Alder Lake chip lacks Thunderbolt capabilities and has a smaller number of integrated graphics cores than the mobile Alder Lake chips do.
Finally, Intel’s Alder Lake will include Intel’s first support for PCI Express 5, announced in 2019. PCIe Gen 5 supports up to twice the bandwidth of PCIe 4, or 64GBps across 16 lanes. That, of course, will be likely gobbled up by both graphics cards and SSDs. An early snapshot of the Alder Lake chipset shows it offering x16 PCIe Gen 5 for graphics cards and a x4 connection to PCIe Gen 4, for SSDs.
Alder Lake’s overall performance remains somewhat of an open question. Remember that Intel’s first attempt at a hybrid processor architecture, Lakefield, came and went with reports of poor performance. We do have the first inkling of how Intel’s performance core will perform, however.
Intel’s new performance core
Intel’s “performance core” or “P-Core” is essentially the legacy of its Core chips, carried forward into Alder Lake. We often refer to Intel’s microprocessors by their code names—Skylake, Rocket Lake—but Intel has its own internal code names for just its CPU cores, too: the little-used “Sunny Cove” codename, for example. Officially, this is “Golden Cove,” but you’ll see it referred to merely as just a performance core. But, according to Intel’s Koduri, this is the core that’s designed for pure speed.
According to Yadi Goaz, the director of the Intel Core CPU architecture, the performance core was designed to step up in general single-threaded CPU performance, but also anticipate the needs of AI and other functions in laptops, desktops, and servers. Intel solved the latter problem with a new AI matrix engine coprocessor. It has a new smart power management controller, too.
While Goaz delved deep into the intricacies of the design, there are a few broad takeways: the P-Core is essentially wider and deeper than before, with the ability to perform better branch prediction for applications with a lot of code. The chip’s caches have been improved to better accommodate data misses. The performance core also integrates a new microcontroller that can examine the needs of applications in a microsecond, even faster than a millisecond. “The result is higher average frequency for any given application,” he said.
Goaz said Alder Lake’s performance core will offer a 19-percent improvement over the “Cypress Cove” core found in Rocket Lake, based on a variety of conventional, current benchmarks: Spec CPU 2017, Sysmark 25, PCMark 10, and more. That comparison is based on running both chips at the same frequency, 3.3GHz. “This level of improvement is even greater than what we delivered with the Sunny Cove core over the Skylake core,” Goaz said.
At the Hot Chips conference on August 23, Intel executives said that the P-Core offers 50 percent more performance over the E-Core, according to the Anandtech live blog of Intel’s presentation.
For new applications, Intel developed a set of new instruction extensions, called Advanced Matrix Extensions, or AMX. AMX was designed for machine learning/AI, both of which have become selling points for hardware for the data center.
Why even develop desktop Alder Lake chips with efficiency cores,? “You’re absolutely right—battery life doesn’t matter in desktop,” said Stephen Robinson, a CPU architect and Intel fellow. “But the thermals do. Fans, cooling power—at some point, you have a limit.”
And that’s why Intel designed its new efficiency cores.
Intel’s new efficiency core
The first thing you need to know about Intel’s efficiency core is that… well, it’s a performance core, too, of a sort. Formerly named “Gracemont,” the Intel efficiency core is essentially a fourth-generation Atom chip that lacks the hyperthreading capabilities of the Intel performance core. “Our primary goal was to build the world’s most efficient X86 core, while still delivering more instructions per clock than Intel’s most prolific architecture to date,” Robinson said.
That architecture was the sixth-generation Intel “Skylake” chip, and Intel’s efficiency core apparently supersedes it in every way. Four of the E-Cores (also manufactured in Intel’s Intel 7 process) take up the die space of a single Skylake core.
The new E-Core also delivers 40 percent more performance than Skylake. If you put four E-Cores against a dual-Skylake system using four threads, you’d still get 80 percent more performance with less power, Robinson said. “We exceed Skylake Core performance by consuming less power in a smaller footprint,” he added.
Intel Thread Director: how it all fits together
Intel’s Thread Director is a thread scheduler, a sort of traffic cop in the operating system, ensuring that high-priority operations are dealt with first, and making sure that a microprocessor isn’t starved for data. Now, with Alder Lake, the question becomes: Which task goes first, and on which processor core type should it run?
That’s the job of the Thread Director, an Intel-designed scheduler specifically designed for Windows 11. Until now, apps running in the foreground (such as the web browser you’re using to read this story) were assigned the highest priority.
Thread Director goes a step further, analyzing the performance needs of each thread, assigning them to the right type of core—and then re-assigning them on the fly if new threads appear. Rajshree Chabukswar, the senior principal Intel engineer in charge of the effort, said Thread Director will manage common consumer tasks like gaming, gaming and streaming, productivity apps, and more. Because Intel Thread Director is running in hardware, not software, developers won’t have to try to assign these priorities themselves.
Interestingly, there may be scenarios where the E-core offers higher performance than the P-Core, and when the P-Core is actually more efficient. The actual frequency these cores will run at will be adjusted by the compute load, and balanced between the different core types. Background threads will run at a low clock frequency, and high-priority threads will run at a higher frequency, Intel said at the Hot Chips conference. All AI workloads will be assigned first to P-Cores, according to the Anandtech live blog.
Some questions remain. For one, there’s the timing: According to Chabukswar, Thread Director support will be incorporated into the “upcoming Windows 11 release,” implying that Windows 11 should support Alder Lake at launch. But it’s still not clear whether Windows 10 will enjoy the same support. Chabukswar said there’s still “hybrid goodness” with Windows 10, but added that Windows 11 will provide the ability to dynamically shift threads back and forth between performance and efficiency cores. It sounds like Windows 10 may lack that capability, making the combination of Windows 11 and Alder Lake that much more efficient.
“The ordering of thread scheduling and other things are taken care of in Windows 10,” Chabukswar said. “Windows 11 takes it to the next level.”
Chabukswar also implied that Alder Lake will run differently on Windows 10 versus Windows 11, but it might not be as straightforward as higher performance scores. Instead, she said a Windows 11 system with Thread Director enabled may be more efficient in bouncing tasks back and forth between the performance and efficiency cores. The results may be hard to quantify: With low-priority tasks handed off to E-cores, will performance improve as the P-Cores are freed up? Or will battery life lengthen? It may all take some testing.
This week, Intel said nothing about Meteor Lake, the eventual successor to Alder Lake. It did, however, close out its Intel Architecture Day with a message from its new chief executive, Pat Gelsinger, reminding everyone to attend Intel Innovation on late October. Could this be a launch party for Intel’s Alder Lake laptops? We hope so.
Updated on Aug. 23 at 9:46 AM with additional detail.
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