P-cores and E-cores in 12th Gen Intel processors: redundant

At the end of October, Intel introduced the 12th generation of Intel Core processors. The main feature of the new chips is the Alder Lake architecture, thanks to which it became possible to place two types of cores in the processor. Intel calls these cores P – Performance and E – Efficiency. Is the move to Alder Lake architecture revolutionary for the desktop segment, or is it pure marketing and not worth the candle? Let’s try to figure it out.

Architecture
It is worth starting with a small introduction to the concept of “large” and “small” kernels. In the 12th generation of processors, Intel adopted the big.LITTLE approach – a similar arrangement of cores in a processor is widely used in the mobile segment. So, almost all chips for mobile devices include powerful and energy efficient cores. For example, the mobile flagship Snapdragon 888 chip has one “super-efficient” ARM Cortex-X1 core, three high-performance (“large”) ARM Cortex-A78 cores, and four energy-efficient (“small”) ARM Cortex-A55 cores.

The big.LITTLE computational architecture was developed by ARM to speed up smartphones and increase their autonomy by saving processor power. However, for some reason, there were no commercially successful big.LITTLE projects for the x86 architecture until this year. But there is scope for “creativity”.

It is in this direction that Intel decided to work in order to send the hackneyed Skylake architecture to a well-deserved retirement. This year, Intel implemented both parts of the old Tik-Tak strategy at once – it switched the processors to the Intel 7 (or 10-nm SuperFin) process technology, which corresponds to Tik, and also introduced a new Alder Lake architecture – Tak.

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Features of cores in Alder Lake
So now it’s clear that Intel has taken the big.LITTLE approach, but what cores are used in Alder Lake? The company answered this question back in August with the presentation of the Golden Cove and Gracemont cores.

Golden Cove is a new high-performance core that replaces Cypress Cove (Rocket Lake). According to the company, Golden Cove provides a 19% increase in IPC (the number of instructions executed per clock) in comparison with Cypress Cove. In addition, delays in low-threaded workloads are reduced.

The layout of the kernel has also undergone significant changes. One Golden Cove core includes an increased L3 cache (1.25 MB per core), 12 execution units, five decoders, a new thread scheduler and a branch predictor. In addition, the L1 cache latency has been reduced and the L2 cache throughput has been optimized.

Gracemont is an efficient core that inherits the Intel Atom ideology. Gracemont is simpler in composition than Golden Cove and has only one thread per core. However, such simplicity of execution allows placing cores in clusters of four on the same area as one Golden Cove core.

Hence the number of cores / threads in the desktop Alder Lake-S, for example, the Core i7-12700K has 12 cores – eight Golden Cove and one cluster with four Gracemont cores.

Gracemont cores are Intel’s most energy efficient cores. According to the company, their single-threaded performance per watt is 40% higher than Skylake, thanks to a number of architectural changes.

In particular, the Gracemont kernels received a 64KB instruction cache and a 32KB data cache. The maximum L2 cache for a cluster is 4 MB. The Gracemont core operates 17 execution ports and two blocks with six decoders for independent code branches. Despite all the improvements, Gracemont kernels cannot execute more than five instructions per clock cycle, which in theory could adversely affect their performance when executing background tasks.

Gracemont kernels are mainly intended for processes that “hang” in the background during normal PC use, for example, messengers, browsers, antiviruses, etc. Also, the majority of tasks are “thrown” to the Gracemont kernels when a new process starts executing on the Golden Cove kernels. An example is rendering and games: if the user starts rendering video, the process will be executed on Golden Cove, but if you launch a video game during rendering, then the former priority task will jump to the Gracemont cores, which will increase the rendering time, although the video game as the main process will run stably. And this is where the magic of interaction between hardware and software begins, or the result of cooperation between Microsoft and Intel – Windows 11 and Thread Director technology.

Thread Director. Windows 11 vs Windows 10
Even before the official presentation of Alder Lake, Intel actively promoted the Thread Director technology, which, apparently, was created in cooperation with Microsoft. Thread Director is a hardware scheduler that distributes processes across threads. You can read more about this technology here . If you don’t want to follow the link, you can watch a demonstration of Thread Director in the video below:

However, the main feature of Thread Director is that the technology works only with Windows 11. Thus, Intel is like telling users: “If you want to fully unleash the processor’s performance, upgrade to Windows 11.” However, is Thread Director really “jerk and break” or is it marketing?

The fact is that Windows has long learned how to distribute processes across cores and threads. However, software has never worked with two types of cores, because such processors simply did not exist. It would seem that this is where Thread Director should come in handy, as a technology created for a new type of processor. In fact, everything turned out to be simpler.

In the large video review of the Core i9-12900K from the Pro Hi-Tech channel, there is an indicative moment with testing the processor with the simultaneous load of Adobe Premiere and Compass 3D. Rendering was launched in the background, and the engineering software was in active mode. As a result, it turned out that in both Windows 11 and Windows 10, rendering was performed on efficient kernels, and Compass 3D worked on productive kernels. The results of this test turned out to be practically the same for both systems. Thus, Thread Director is either another marketing lure, or a technology for the future.

By the way, the fact that Alder Lake works the same on Windows 10 and Windows 11 was confirmed by the authoritative Gamers Nexus channel (1.5 million subscribers) in its review .

However, there is still a reason to use Alder Lake with Windows 11 – memory lag. In Windows 11, these latencies are reduced by more than 20%. At least Pro Hi-Tech has achieved just such results with overclocked DDR5-5600 modules with timings of 40-39-39-72. By the way, the reduced memory latency had almost no effect on the execution time of tasks and FPS in games.

Known Issues
Intel has certainly made a new product for the desktop PC market. However, not all software turned out to be ready for the big.LITTLE architecture. So, right after the release of Alder Lake to the market, users noticed that some games did not run on systems with new processors.

It turned out that the energy-efficient cores interfered with the launch of DRM-protected Denuvo games, causing various crashes – Intel reported this on its blog . Fortunately, the problem was quickly resolved through Denuvo’s efforts.

Other known issues are not as critical and, if they arise, are quickly fixed by software developers. For example, in synthetic tests Cinebench R15 Core i9-12900K showed an abnormally low result of multi-threaded performance in Windows 10 – 1223 points. Whereas the normal values ​​in this test are at 4000 points.

Output
So it’s time to summarize the Alder Lake lineup. Yes, Intel has made an interesting product with an architecture unusual for a desktop. However, a number of problems, including the “raw” architecture, DDR5 with high latencies and unoptimized software in places, can darken the impression of using the new processors. Also, don’t forget about the price-performance ratio. Considering the price of DDR5 , Z690 motherboards and Alder Lake processors themselves, buying such a system may not be entirely justified now.

However, if you ignore all these factors, then the Alder Lake series processors are the undisputed leaders in performance, each in its segment, and the Core i9-12900K is the most productive processor in almost all modern games and applications.

Only those who are not afraid to become a beta tester of the new memory standard and big.LITTLE desktop architecture can recommend a system based on Alder Lake and DDR5. In addition, for Alder Lake, it is still desirable to work under Windows 11, since even with Thread Director (albeit a fake one) it is clear that Intel completely and completely prefers the new OS. Most likely, in the future, patches will be released that will further optimize the operation of Alder Lake and DDR5 under Windows 11.

And if you don’t like becoming a beta tester for your money, then you can pay attention to other current processors from the Intel Core 10 th / 11 th Gen and Ryzen 3000/5000 lines .

As for whether it was the right decision, it is difficult to say now to split the cores in a desktop processor. Intel made its product unique, as AMD once did, introducing Ryzen with a chipset architecture and more cores for the time. Intel’s new architecture will definitely bear fruit, if not in this generation, then in the future.