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ARM aims speedy, power-stingy Cortex-A12 at mid-range mobiles

Jun 3, 2013 — by Eric Brown 849 views

ARM announced a 28nm-fabricated Cortex-A12 processor design claimed to offer 40 percent higher performance than the Cortex-A9, while drawing the same power. The Cortex-A12 is paired with a power-efficient Mali-T622 GPU and Mali-V500 video coprocessor, and supports hybrid Big.Little SoC configurations in partnership with the Cortex-A7.

Billed as a successor to the popular Cortex-A9 processor, the similarly ARMv7 Cortex-A12 design advances to a 28nm process that offers 40 percent faster performance in the same power envelope, claims ARM. Despite these advances, and the ability to support up to four cores, it is billed as a processor targeting the “580 million mid-range smartphones and tablets forecast to be sold in 2015.”

The high range for mobile would appear to belong to the Cortex-A15, as well as the upcoming ARMv8-based Cortex-A53, due in 2014. The latter will be able to work as the slower, more power efficient member of a Big.Little combo system-on-chip (SoC) that will include the similarly 64-bit Cortex-A57, which is primarily aimed at laptops and micro-servers.


ARM Cortex-A12 block diagram


After the Cortex-A12 ships in tablets and smartphones in late 2014, a subsequent version will be able to replace Cortex-A15 SoCs in Big.Little hybrid chipsets with the Cortex-A7. Such hybrids would provide somewhat slower performance than an A15-driven Big.Little combo like the Samsung Exynos 5 octa, but would offer a smaller footprint and better battery life.

The first Cortex-A12 based mobile devices are due in late 2014, no doubt in the form of upcoming system-on-chips (SoCs) from typical licensees like Nvidia, Samsung, Texas Instruments, and Freescale. Interestingly, however, the only supplied testimonial was from Via Technologies, a longtime x86 processor vendor that has increasingly moved into ARM designs.

In addition to mobile devices, other potential device targets include DTV and home networking equipment, says ARM.

Support for 1TB memory, virtualization, and TrustZone

The Cortex-A12 offers far better memory support than the Cortex-A9, providing 1TB addressable memory space via LPAE (Large Physical Address Extensions) 40-bit addressing capability, says ARM. Memory handling is also enhanced with Thumb-2 technology, which is said to require 30 percent less memory for storage. The processor design also adds virtualization and TrustZone security technologies.

Additional features are said to include integrated L2 cache with support for up to 8MB cache and high-reliability options. The Cortex-A12 also supplies a peripheral port for low-latency peripheral accesses, as well as an Accelerator Coherency Port (ACP), both said to be compatible with the processor’s 128-bit AMBA 4 AXI bus interface.

No projected clock rates were mentioned, but the 40 percent better performance is said to be due to the 28nm process and improved VFPv4 floating point unit (FPU) capabilities, which include hardware support for floating-point operations in half-, single- and double-precision FPU arithmetic. Performance is also boosted via ARM cores that are tightly integrated with NEON/FPU, says ARM.

According to an Anandtech report the tight Neon/FPU integration with the ARM cores refers in part to the fact that the Cortex A12’s dual-issue out-of-order architecture, unlike that of the Cortex A9, is “fully out-of-order including the NEON/FP units.” Pipeline length has also increased “a bit” to 11 stages, compared to Cortex-A9, says Anandtech, and the execution back end has improved somewhat.

ARM makes no power consumption claims for the processor in general. Yet, assuming the Cortex-A12 processor can run 40 percent faster than a Cortex-A9, it should theoretically be able to offer roughly 40 percent lower power consumption if performance stays constant.

Power-stingy Mali-T622 GPU and Mali-T622 video IP

The Cortex-A9’s ARM-approved GPU pairing is with ARM’s Mali-T622 GPU IP. ARM calls the OpenGL ES 3.0 compatible Mali-T622 “the smallest OpenCL 1.1 Full Profile solution,” and says it offers 50 percent better energy efficiency over the Mali-T604.

Mali-T622 GPU and Mali-V500 video coprocessor block diagrams
(click images to enlarge)


The recommended Cortex-A9 SoC design also includes a new video coprocessor called the Mali-V500. Like the Mali-T622, the chip is touted for its small size and low power consumption. The Mali-V500 is said to be compatible with ARM’s TrustZone security technology. It offers 1080p60 resolution on single-core processors, or up to 4k resolution at 120fps on eight cores, says ARM. The SoCs based on the Cortex-A12, however, are limited to quad-core designs.

The Cortex-A12 will be supported with typical ARM development tools like its 28nm-compatible ARM POP IP, which features Artisan physical IP. Also available is the ARM DS-5 toolchain and ARM Fast Models simulation library.

More information may be found on the ARM Cortex-A12 page.

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