ARM Cortex-A15

ARM Cortex-A15

Produced	In production late 2011,[1] to market late 2012[2]
Designed by	ARM Holdings
Max. CPU clock rate	1.0 GHz  to 2.5 GHz
Min. feature size	32 nm/28 nm initially[3] to 22 nm roadmap[3]
Microarchitecture	ARMv7-A
Cores	1–4 per cluster, 1–2 clusters per physical chip[4]
L1 cache	64 KB (32 KB I-cache, 32 KB D-cache) per core
L2 cache	Up to 4 MB[5] per cluster
L3 cache	none

The ARM Cortex-A15 MPCore is a 32-bit processor core licensed by ARM Holdings implementing the ARMv7-A architecture. It is a multicore processor with out-of-order superscalar pipeline running at up to 2.5 GHz.^[6]

Overview

ARM has claimed that the Cortex-A15 core is 40 percent more powerful than the Cortex-A9 core with the same number of cores at the same speed.^[7] The first A15 designs came out in the autumn of 2011, but products based on the chip did not reach the market until 2012.^[1]

Key features of the Cortex-A15 core are:

• 40-bit Large Physical Address Extensions (LPAE) addressing up to 1 TB of RAM.^[8][9] As per the x86 Physical Address Extension, virtual address space remains 32 bit.^[10]
• 15 stage integer/17–25 stage floating point pipeline, with out-of-order speculative issue 3-way superscalar execution pipeline^[11]
• 4 cores per cluster, up to 2 clusters per chip with CoreLink 400 (CCI-400, an AMBA-4 coherent interconnect) and 4 clusters per chip with CCN-504.^[12] ARM provides specifications but the licensees individually design ARM chips, and AMBA-4 scales beyond 2 clusters. The theoretical limit is 16 clusters; 4 bits are used to code the CLUSTERID number in the CP15 register (bits 8 to 11).^[13]
• DSP and NEON SIMD extensions onboard (per core)
• VFPv4 Floating Point Unit onboard (per core)
• Hardware virtualization support
• Thumb-2 instruction set encoding to reduce the size of programs with little impact on performance
• TrustZone security extensions
• Jazelle RCT for JIT compilation
• Program Trace Macrocell and CoreSight Design Kit for unobtrusive tracing of instruction execution
• 32 KB data + 32 KB instruction L1 cache per core
• Integrated low-latency level-2 cache controller, up to 4 MB per cluster

Chips

First implementation came from Samsung in 2012 with the Exynos 5 Dual, which shipped in October 2012 with the Samsung Chromebook Series 3 (ARM version), followed in November by the Google Nexus 10.

Press announcements of current implementations:

• Broadcom SoC^[14]
• HiSilicon K3V3^[15]
• Nvidia Tegra 4 (Wayne)^[16] and Tegra K1.
• Samsung Exynos 5 Dual, Quad and Octa^[17]
• ST-Ericsson Nova A9600 (cancelled) (dual-core @ 2.5 GHz over 20k DMIPS)^[18][19]
• Texas Instruments OMAP 5 SoCs^[20] and Sitara AM57x family^[21]

Other licensees, such as LG,^[22][23] are expected to produce an A15 based design at some point.

Systems on a chip

See also

• ARM architecture
• List of ARM cores
• List of applications of ARM cores
• Comparison of ARMv8-A cores
• JTAG

References

External links

• Official website
• ARM Cortex-A15 Technical Reference Manuals