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Samsung’s Cortex-A15 SoC enables tablets with 2560 x 1600 resolution

Nov 30, 2011 — by Eric Brown — from the LinuxDevices Archive — 4 views

Samsung has begun sampling its first ARM Cortex-A15 processor, aimed at high-end tablets and capable of supporting resolutions up to 2560 x 1600 pixels. Scheduled for production in 2Q 2012, the Exynos 5250 is equipped with two Cortex-A15 cores clocked at 2GHz, providing what the company says is four times the graphics performance of its previous top model.

Samsung's Exynos 5250 is the company's first system on chip (SoC) to adopt ARM's high-end Cortex-A15 architecture, which targets everything from smartphones to servers. Texas Instruments and ST-Ericsson, too, have announced Cortex-A15 SoCs — neither of which has gone into production — and Nvidia and LG have said they're prepping A15 models of their own. (See farther below for more on the A15 competition, as well as technical details on the A15 architecture itself.)

Exynos 5250

Samsung claims its Exynos 5250 will offer twice the processing performance of its previous top model, the dual-core, 1.5GHz Cortex-A9 based Exynos 4212. Specifically, the Exynos 5250 is said to provide 14,000 DMIPS versus the 7,500 DMIPS for the Exynos 4212. (The 4212, set to begin sampling by the end of the year, follows the earlier dual-core, 1.2GHz Exynos 4210 that's used in the Samsung Galaxy S II phones, among other Android-based mobile devices.)

Like the 4212, the 5250 moves up to a 32nm, low-power HKMG (High-K Metal Gate) process, bringing performance and power efficiency improvements. Samsung also claims the Exynos 5250 offers four times the 3D graphics performance of Cortex-A9 SoCs.

Like other Cortex-A15 processors, including TI's OMAP5, the SoC supports stereoscopic 3D displays, and it also boosts display resolution to up to WQXGA (2560 × 1600 pixels), or over twice the size of typical 10-inch tablet displays, claims the company. The greater resolution is partially enabled by a memory bandwidth that has been doubled to 12.8 Gigabytes per second (GB/s) compared to current, 6.4GB/s dual-core processors, claims Samsung. This is said to help speed overall processing 3D graphics, and HD displays.

The Exynos 5250 also features an embedded DisplayPort (eDP) interface said to be compliant with the SoC's panel self-refresh technology (PSR), applied to the timing controller (T-CON). The PSR technology enables static images to be refreshed directly from the T-CON's frame buffer memory, according to Samsung. As a result, the SoC does not need to send regular display refresh instructions when reading static web pages or e-books, thereby saving on battery life, says the company.

In addition, the SoC supplies an embedded image signal processor, said to enable eight-megapixel images at 30 frames per second (fps). Meanwhile, a video hardware codec engine offers 1080p 60fps video recording and playback, says the company.

Peripheral highlights include an HDMI 1.4 interface, as well as bootable device interfaces such as SATA, UART, and USB, according to Samsung. External ports are said to include USB 3.0, eMMC 4.5, and eSD 3.0.

Other Cortex-A15 SoCs

Following ARM's Sept. 2010 announcement of the Cortex-A15 processor design, Texas Instruments (TI) got the ball rolling by announcing the first A15-based SoC with the OMAP5430 and OMAP5432. Like the Exynos 5250, these dual-core OMAP5 models are clocked to 2GHz. Scheduled to begin sampling during the second half of 2011, they offer support for up to four cameras, HD video encode/decode in 2D or 3D, imaging up to 24 megapixels, and Kinect-like gesture support, according to TI.

Another home for Cortex-A15 IP has been announced by ST-Ericsson, which said in February that its Nova A9600 will begin sampling sometime this year. The 28nm-fabbed A9600 will offer dual cores clocked at up to 2.5GHz, plus Imagination Technologies' Series6 ("Rogue") graphics IP, giving it the ability to play full HD video at up to 120fps, the company said.

In January, Nvidia announced it had licensed the Cortex-A15 core for future-generation Tegra processors, but offered few details. Other announced A15 licensees include LG Electronics.

Cortex-A15 background

ARM's Cortex-A15 architecture targets 32nm and 28nm fabrication processes, and supports up to four cores at clock rates at up to 2.5GHz, says ARM. Other touted features include enhanced virtualization support, 1TB memory access, plus up to five times the performance of current smartphone processors — all with similar power consumption — claims ARM.

The Cortex-A15 MPCore processor is equipped with an out-of-order superscalar pipeline, along with a tightly-coupled low-latency level-2 cache of up to 4MB, according to ARM. The processor can decode and dispatch up to three instructions per cycle, says the company. This is said to be three times the rate possible with an ARM11 processor.

In addition, the Cortex-A15 can issue up to eight instructions per cycle, and take less than 10 microseconds to move into standby or wake up again. Floating point and NEON instruction set performance for signal processing and multimedia have also been improved, says ARM.

LPAE will let ARM Cortex-A15 CPUs work with physical memory up to 1TB

(Click to enlarge)

Compared to the Cortex-A9, the Cortex-A15 adds more efficient hardware support for operating system (OS) virtualization, soft-error recovery, larger memory addressability, and system coherency, says ARM. Large Physical Address Extensions (LPAE), shown in the diagram above, is said to permit addressing up to 1TB of memory.

The Cortex-A15 is claimed to be the first ARM processor to incorporate highly efficient hardware support for data management and arbitration. This hypervisor support enables multiple virtual software environments and their applications to simultaneously access system capabilities while remaining isolated from each other, says the company.

With quad-core Cortex-A9 processors just now arriving, led by Nvidia's Tegra 3, it is uncertain how soon the Cortex-A15 will dominate the tablet or smartphone markets. Meanwhile, ARM has received considerable interest from server SoC vendors looking to fill the need for more power efficient servers. Although Calxeda has developed a quad-core Cortex-A9 ECX-1000 "server on a chip," many believe the A15 is the processor that will offer the first significant competition with Intel and AMD in the server space.

One interesting use for the Cortex-A15 was revealed by ARM when it recently unveiled its Cortex-A7 — the heir to the Cortex-A8. According to ARM, the Cortex-A7 can be deployed along with the Cortex-A15 in a "big.Little" SoC design that interconnects the two at 20 microsecond speeds.

The lower-power Cortex-A7 would be used for basic tasks like social media, audio playback, telephony, and running an operating system. The Cortex-A15 would be used for the more compute intense workloads, such as navigation and gaming. Power management software would select the right processor for the right jobs in a fashion that would be transparent to the user, enabling up to a 70 percent extension in battery life, claims ARM.

Stated Dojun Rhee, vice president of System LSI marketing, Device Solutions, Samsung Electronics, "The ARM Cortex-A15 brings unparalleled performance to our Exynos processor family and the exploding mobile marketplace."


The Exynos 5250 is currently sampling to customers and is scheduled for mass production in the second quarter of 2012, says Samsung. An English language version of the Samsung press release may be found here.

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