New smartphone- and laptop-CPUs

arm unveiled Cortex-A roadmap by 2020

16. August 2018, 15:00 Uhr | Frank Riemenschneider
SPICE-Simulationen auf dem iPad realisieren und gleich mit anderen Anwendern – z.B. mit Laptop ausgerüstet – teilen: „Multisim Touch"
arm wants to lose Intel market share in the laptop market. Cortex-A processors should provide the necessary computing power.
© National Instruments

For the first time in its company history arm unveiled a long-term roadmap for its Cortex-A CPUs. Details for the next two generations remained largely on the surface, but interesting comparisons to current Intel chips were made.

In the field of mobile phones, it is well known that nothing works without arm CPU cores for a long time now. In addition to designing in the original arm IP cores with the designation Cortex-A, there are also customer-designed CPUs based on the armv8-A microarchitecture with the help of so-called arm architecture licenses, which are installed by Apple and Samsung, for example.

After the greatest growth times in mobile phones are over, arm is now concentrating on new markets, including the laptop computer, which is dominated by Intel with its x86 CPUs. Today, arm's market share is negligible, so of course the theoretical growth opportunities are all the higher, provided you have the right products.

The first arm CPU that can actually keep up with the computing power requirements of a laptop was the Cortex-A76 presented at arm TechDays in Austin in 2018, which we have already presented in detail technically (german article).

A comparison of a 3 GHz Cortex-A76 with 4 MB L3 cache and an Intel Core-i5-7300U of the current Kaby Lake generation with the benchmark SPECINT2 shows that the Cortex-A76 exceeds the Intel CPU in its baseline configuration (2.6 GHz clock frequency) in terms of computing power and remains only marginally behind in the turbo mode of the Core-i5 (3.5 GHz clock frequency). While a complete A76-SoC for a laptop, where besides CPU there are other blocks like GPU, video, I/Os etc., should consume less than 5 W, the Core i5-7300U has a nominal TDP of 15 W, whereby the power consumption can vary between 7.5 and 25 W depending on the operating point (the basic clock frequency can be configured between 800 MHz and 2.7 GHz). A corresponding slide is shown in the picture gallery.

To be fair, SPECINT2 maps a single-thread scenario, while the official Intel data is based on a multi-thread workload. Under the given conditions we consider approx. 11 W more realistic, which of course should not diminish the higher energy efficiency of the Cortex-A76, but let the data of arm appear in a different light. Interesting in this context is also to see that arm has reduced its power consumption projection from TechDay. While 5 W was seen at 3.3 GHz for the Cortex-A76 at the time, "less than 5 W" is now spoken of at 3 GHz.

To be fair it has to be also said that arm has cleverly chosen the comparison CPU: Firstly, the Core-i-5-7300U comes from the Kaby Lake generation and not from the newer Coffee Lake generation, which is less relevant since the IPC (instructions per clock cycle) remained unchanged from Koby Lake. What is more important is that arm has now chosen a very weak representative of all available CPUs. In the CPU test of the colleagues at Chip magazine, the Core-i-5-7300U provides just 35.3% of the computing power of the mobile CPU leader Intel Core i7-8750H. However, the latter also has three times as high TDP at 45 W, so that arm’s energy efficiency advantages remain independent of the Intel model. The question is, however, whether the Cortex-A76 provides enough absolute computing power to enable the laptop user to work comfortably - the colleagues of the chip have given the Core-i5-7300U a devastating testimony: "The mobile processor Intel Core i5-7300U is rather weak in the test lab..... Within our extensive laboratory tests, the device cannot excel in any single evaluation. We can even detect a significant drop-out during our tests."

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arm unveils Cortex-A roadmap up to 2020

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New CPUs in 2019 and 2020

Since it is also clear to arm that significant gains in laptop market share require further increases in computing power, the next two cores were announced: In 2019, "Deimos", which will be manufactured by TSMC & Co. in the then finished 7 nm processes, and in 2020 "Hercules" in an expected 5 nm. arm has not yet announced technical details about both CPUs, except that Hercules will have 2.5x such a high computing power as the Cortex-A73 introduced in 2016. This goal is to be achieved through a further increase in IPC through improvements to the microarchitecture, optimizations to the memory system and, of course, the shrunken manufacturing process geometries. arm will unveil further details at its developer conference TechCon in October. Both future CPUs will be based on the new A76 microarchitecture and will receive corresponding evolutionary refinements.

Arm expects that the introduction of the 5G wireless standard will bring out more allways-on- and allways-connected laptops, where energy efficiency will naturally play an even more important role than today. Since arm will continue to supply IP for smartphones and computers, the design will (must) continue to be geared to the needs of a smartphone in terms of absolute power consumption and Intel will thus, as can already be predicted today, be clearly undercut. The question will be whether it will be possible to provide the absolute computing power required for user needs. Since arm itself has certified a Cortex-A76 to have a SPECint2K value 1.58 times higher than the Cortex-A73, this means that "Hercules" will also have a value about 1.58 times higher than the Cortex-A76 (1.58x1.58=2.5). This would then be almost 60% of the computing power of the high-end Intel Core i7-87750H and would correspond to a current Intel Core i7-4710HQ.

In my personal experience you can work very well with such a laptop in most cases. The Intel Core i7-4710HQ was installed even in a notebook "ASUS Gaming GL551JK", whose target group is at the upper end of the performance scale.

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