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64-bit ARMv8 architecture to debut in Applied Micro X Gene SoC

Oct 27, 2011 — by Eric Brown — from the LinuxDevices Archive — 2 views

ARM has announced its ARMv8 architecture, featuring 64-bit instruction set support, extended virtual addressing, and backwards-compatible 32-bit support. Meanwhile, Applied Micro used the ARM TechCon event to demonstrate core functionality of its “world's first” ARMv8 implementation, the server-targeted X-Gene — touted as featuring 28nm fabrication, up to 128 cores, 3GHz clock rates, 300mW standby consumption, and 64-bit Linux support.

ARM's announcement of its Cortex-A7 prefaced this week's ARM TechCon conference and dominated the event, but ARM had another showstopper saved up for the last day. The processor design firm announced a new ARMv8 architecture Oct. 27 it says will bring energy-efficient 64-bit computing to new applications such as high-end servers and computing.

While introducing a 64-bit instruction set, ARMv8 also offers 32-bit support for backwards compatibility with today's ARMv7 processor designs, such as the Cortex-A8, -A9, -A7 and high-end Cortex-A15. (See farther below for more background.)

As we report later in this story, Applied Micro has already announced a server-centric ARMv8 implementation. Others will be announced in 2012, and actual server prototypes running on the new architecture are expected in 2014, according to ARM.

Indeed, servers seem to be a major focus, with Nvidia stepping forward to suggest it plans to offer a server-oriented ARMv8 SoC in the future. ARMv8 will also gradually replace ARMv7 in consumer electronics and mobile devices as well, says ARM.

Two main execution states

The ARMv8 architecture offers two main execution states. The AArch64 state introduces a new A64 instruction set for 64-bit processing, while the AArch32 state supports the existing 32-bit ARM instruction set, says ARM. ARMv8 will also maintain or extend ARMv7 features like TrustZone, virtualization, and NEON advanced SIMD, says ARM.

ARM plans to help develop a "robust design ecosystem" to support the 64-bit instruction set. ARMv8 versions of the ARM compiler and Fast Models have already been made available to key ecosystem partners, says the company. Meanwhile, initial support for a range of open source operating systems, applications, and third-party tools is already said to be in development.

ARM did not offer any further details, although an EETimes report covering the ARM TechCon event quoted ARM Chief Technology Officer Mike Muller as saying: "A 64-bit OS can easily and efficiently support existing 32-bit software."

Muller also took a swipe at arch-rival Intel, whose x86 architecture has offered 64-bit support for years, helping it dominate the server processor market. The future, he was quoted as saying, would be won by designs offering "lots of power efficient cores rather than some more power inefficient cores."

ARM has pushed the multicore, 2.5GHz Cortex-A15 design as a suitable server platform, and reportedly signed up HP for upcoming servers based on lower-powered, quad-core Cortex-A9 processors. However, the lack of 64-bit support and other server-oriented features is a deal-breaker for many applications. If ARM can match 64-bit support with its typical power consumption advantage, the server industry may well stray from the Intel and AMD fold.

Applied Micro X Gene is first up to bat

Applied Micro — known for its PowerPC processors, such as its PacketPro system on chips (SoCs), announced the X Gene — billed as "the world's first 64-bit ARM architecture compliant processor." X Gene will scale to as many as 128 cores, at clock rates of up to 3GHz, says the company. It's said to target next-generation cloud computing, wireless infrastructure, enterprise networking, storage and security applications.

The first X Gene SoC design will be optimized for cloud server systems, and will be based on a "sophisticated microarchitecture" for the ARMv8 64-bit ISA, says AppliedMicro. Delivering "unparalleled single-thread performance, full CPU and I/O virtualization," the X Gene will reduce server cost, power, and complexity by more than 50 percent, claims the company.

The X Gene combines "server-class" dynamic power management with the ability to configure thermal dissipated power (TDP) to meet varying requirements, says AppliedMicro. Standby power will run on less than 300mW, a figure the company refers to as "unprecedented."

Multiple 64-bit ARMv8 cores will be interconnected via a "terabit coherent fabric" with on-chip 10-gigabit Ethernet (10GbE), storage, and WAN physical layer IP, says AppliedMicro. The X Gene will also feature a 100 gigabit per second inter-socket communications interface "to extend coherency to multi-chip configurations," says the company.

The SoC will integrate Reliability, Availability and Serviceability (RAS) features required in the server space, says the company. In addition, a server class open-source OS will be fully enabled by the time of production.

First samples of AppliedMicro's ARMv8-based X-Gene SoCs are expected in the second half of 2012 and will be produced at TSMC in both 40-nanometer (nm) and 28nm process technologies, says the company.

Meanwhile, Applied Micro used ARM TechCon to demonstrate "core functionality" of the X Gene via a Xilinx Virtex-6 FPGA, with UBoot and 64-bit Linux. The demonstration platform showed of the ARM-64 CPU complex, a coherent CPU fabric, high performance I/O network, and a memory subsystem, along with fully functional SoC subsystem, says the company.

ARM architecture background in a nutshell

The first widely adopted ARM architecture was ARMv5, which powers the ARM926EJ-S core. This was followed by ARMv6, which runs the circa-2003 ARM1176JZ-S core, enabling multicore support. ARMv7 debuted in 2005 with the single-core Cortex-A8 design. ARMv7 then went multicore with the addition of the previously announced MPCore technology, which debuted in the Cortex-A9 design announced in 2009. The Cortex-A15 and new Cortex-A7 processors also run on ARMv7.


The ARMv8 architecture specifications describing all aspects of the ARMv8 architecture are available now to partners under license. ARM will disclose processors based on ARMv8 during 2012, with consumer and enterprise prototype systems expected in 2014.

First samples of AppliedMicro's ARMv8-based X-Gene SoCs are expected in the second half of 2012 and will be produced at TSMC in both 40-nanometer (nm) and 28nm process technologies, says the company. Meanwhile, ecosystem support for the FPGA X Gene emulation platform, including performance metrics, will be available for customer evaluation by the first half of 2012, says AppliedMicro. More information may be found in this X Gene announcement.

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