ARM Unveils Cortex-A75, A55 Processors And Mali-G72 GPU

By | 30th May 2017

ARM has officially announced three new products that surely will make their way into next-generation mobile devices. The company presented its new products right before the COMPUTEX event that will be held in Taipei between May 30 to June 3.

ARM’s portfolio is now expanded with the high-performance the Cortex-A75 microarchitecture and  the energy-efficient Cortex-A55. In addition to these two products, ARM presented its high-end Mali-G72 GPU. The Cortex-A75 and A55 are the first DynamiQ CPUs from ARM.

The new most powerful CPU from ARM, the Cortex-A75, is a successor to the Cortex-A73 which we begin to see in phones this year. The latter has been announced exactly one year ago, also during the COMPUTEX event. This new latest product from ARM supports the ARMv8-A architecture and is designed to be implemented in a diverse range of devices, including smartphones and tablets. As usual, the producer focused on bringing yet more performance and minimize energy consumption. ARM believes that the Cortex-A75 outperforms Cortex-A73 in most metrics, including up to 20% in integer core performance. The CPU also provides extra performance for advanced and specialized workloads, like machine learning.

ARM has also introduced a new memory sub-system. Among new features, ARM mentions access to the shared cluster L3 cache, support for asynchronous frequencies, and potentially independent voltage and power rails for each CPU or groups of cores. The Cortex-A75 CPU also uses a private L2 cache per core with half the latency of  those in the A73. These changes directly translate into better performance, and although these specific gains won’t show up everywhere, in advanced use cases the A75 chip can be 48 percent faster than its predecessor.

Note that the scale of ARM’s graphs is misleading, pay attention to the multipliers and not the length.

The latest high-end CPU from ARM can also be used on devices with large screens. The British company opened a dedicated Large Screen Compute division a year and a half ago and wants to tackle on the segment, where Intel king. ARM did a major architectural change with the A75 and opened a larger power envelope for chips using this core, with power consumption now being scaled to 2W. As a result, a laptop would get 30 percent of extra performance, according to ARM.

Below you can see a full technical specification of the newest ARM’s frontrunner.

GeneralArchitecture ARMv8-A (Harvard)
Extensions ARMv8.1 extensions

ARMv8.2 extensions

Cryptography extensions

RAS extensions

ARMv8.3 (LDAPR instructions only)

ISA Support A64, A32 and T32 instruction sets
MicroarchitecturePipeline Out-of-order
Superscalar Yes
NEON / Floating Point Unit Included
Cryptography Unit Optional
Max number of CPUs in cluster Four (4)
Physical addressing (PA) 44-bit
Memory System and External InterfacesL1 I-Cache / D-Cache 64KB
L2 Cache 256KB to 512KB
L3 Cache Optional, 512KB to 4MB
ECC Support Yes
LPAE Yes
Bus interfaces ACE or CHI
ACP Optional
Peripheral Port Optional
OtherFunctional Safety Support ASIL D
Security TrustZone
Interrupts GIC interface, GIVv4
Generic timer ARMv8-A
PMU PMUv3
Debug ARMv8-A (plus ARMv8.2-A extensions)
CoreSight CoreSightv3
Embedded Trace Macrocell ETMv4.2 (Instruction trace)

Cortex-A75 and A55 are the first DynamIQ big.LITTLE CPUs from ARM. DynamIQ also enables new flexible combinations for vendors. The standard half+half with multicluster combination can be replaced with 1+7 or 2+6 — in essence, SoC vendors can decide whether they want to use more big or LITTLE CPUs within a single cluster. New processors have been redesigned with a new essential DynamIQ Shared Unit (DSU), which is tasked with power management, ACP and peripheral port interfacing. They also feature the L3 cache for the first time for ARM’s mobile processors. It’s important to mention that both A55 and A75 are built on the company’s latest ARMv8.2-A architecture. This makes them incompatible with any other processors including A73 and A53.

The smaller Cortex-A55 is a long time replacer of the Cortex-A53. The latter has been shipped on 1.7 billion devices over last three years, and you’ve probably come across it as it’s been featured in both budget devices and flagships alike. The new A55 is set to be placed in most smartphones in the foreseeable future. The Cortex-A55 has the highest power efficiency of any mid-range CPUs designed by ARM. In fact, it uses 15 percent less energy than Cortex-A53. Finally, ARM claims that the newest LITTLE cores are the most powerful mid-range units. It also features the latest architecture extensions that introduce new NEON instructions for machine learning, advanced safety features and more support for Reliability, Accessibility and Serviceability (RAS).

Full specifications of the Cortex-A55 are available below.

General Architecture ARMv8-A (Harvard)
 Extensions ARMv8.1 extensions

ARMv8.2 extensions

Cryptography extensions

RAS extensions

ARMv8.3 (LDAPR instructions only)

 ISA Support A64, A32 and T32 instruction sets
 Microarchitecture Pipeline In-order
 Superscalar Yes
 NEON / Floating Point Unit Optional
 Cryptography Unit Optional
 Max number of CPUs in cluster Eight (8)
 Physical addressing (PA) 40-bit
 Memory System and External Interfaces L1 I-Cache / D-Cache 16KB to 64KB
 L2 Cache Optional, 64KB to 256KB
 L3 Cache Optional, 512KB to 4MB
 ECC Support Yes
 LPAE Yes
 Bus interfaces ACE or CHI
 ACP Optional
 Peripheral Port Optional
 Other Functional Safety Support Up to ASIL D
 Security TrustZone
 Interrupts GIC interface, GIVv4
 Generic timer ARMv8-A
 PMU PMUv3
 Debug ARMv8-A (plus ARMv8.2-A extensions)
 CoreSight CoreSightv3
 Embedded Trace Macrocell ETMv4.2 (Instruction trace)

Moving on to the GPU, ARM has also prepared a new product. The Mali-G72 is a successor of the G71, which has also been featured in 2017 SoCs in a variety of configurations, due to its remarkable scalability. The new GPU, though, offers 20 percent better performance density, which means that manufacturers can use more GPU cores in the same die area. It’s estimated that smartphones will use up to 32 shader cores as a maximum. Additionally, the new GPU will use 25 percent less energy, and it is also improving in terms of machine learning efficiency — ARM claims it’s showing itself to be 17 percent better than the G71 in ML benchmarks.

SoC vendors should begin implementing ARM’s new portfolio in their new generations. We should expect devices using ARM’s hardware early next year at the latest, possibly during Mobile World Congress in Barcelona.


Source: ARM [1] Source: ARM [2]