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MontaVista adds big-endian ARM11 port

Dec 15, 2008 — by Eric Brown — from the LinuxDevices Archive — 2 views

[Updated: 3PM] — MontaVista announced what it calls the “first-ever” support in a Linux environment for ARM11 processors in big-endian mode. Presumably, the big-endian port of MontaVista Linux opens the door to more IPv6-friendly mobile devices, or greater use of ARM in telecommunications, where big-endian has long been standard.

MontaVista says its big-endian ARM11 port works on Freescale i.MX3x SoCs with ARM1176JZ-S and ARM1176JZF-S cores, which were announced in late 2003 and shipped in 2004. (See below for more information.)

In announcing the port, MontaVista called attention to its claim of having the only mobile Linux distribution certified to support IPv6. Among other benefits, Linux's IPv6 support can increase battery life in mobile devices, by obviating the frequent “keep-alive” messages that devices behind an ipmasq (NAT) firewall are required to send. MontaVista also noted that its Linux kernels power “a majority of today's Linux handsets.”

Like many other RISC architectures, ARM is bi-endian, and thus can be configured to access data either from left-to-right (big endian) or right-to-left (little endian). MontaVista supports both modes in the following varieties, wrote a company spokesperson in an email:

  • arm_v6_be — big endian
  • arm_v6_le — little endian
  • arm_v6_vfp_le — virtual floating point little endian
  • arm_v6_vfp_le_uclibc — virtual floating point little endian, micro C- library

Traditionally, little endian mode has been favored over big endian because it simplifies bit-wise math. The most mature ARM Linux ports arguably use little-endianness. However, big endian (also called “network order,” according to Wikipedia) is used in Internet Protocol, as well as in telecommunications systems, because it is said to enable faster routing of compressed data.

According to the spokesperson, as far as he knows, the company is the only Linux commercialization vendor supporting both big and little endian modes for ARM11. Big-endian has been adopted for ARM11 processors by products such as the Texas Instruments Puma5 cable modem processor, “which has gotten a lot of attention and activity in the market,” said the spokesperson.

Going mobile: the ARM1176JZx

Both the ARM1176JZ-S and ARM1176JZF-S cores are based on the ARMv6 instruction set implemented in ARM11 cores, and the JZF-S version offers a floating-point coprocessor. The cores were said to be the first to offer ARM's TrustZone security technology, as well as the first to offer its Intelligent Energy Manager firmware.

In 2006, ARM released a faster, lower-power die-shrunk version of the JZF-S, targeting SoCs fabricated using 90nm rather than the older 0.13-micron processes. The new version can be clocked to 750MHz (up from 550MHz), and boasts lower power draw, claimed to be under 500mW.

The ARM1176JZF-S is featured in STMicroelectronics's STn8820 SoC, designed for running HD video on mobile devices, as well as Freescale's new i.MX37 SoC, which is aimed at the portable media player (PMP), mobile Internet, and personal navigation device (PND) markets.

Freescale's older i.MX31, meanwhile, uses the ARM1176JZ-S version of the core. In June of this year, MontaVista announced that its Mobilinux 5.0 version of MontaVista Linux had been optimized for the i.MX31.

Stated Patrick MacCartee, director of product management at MontaVista, “ARM is constantly pushing the envelope when it comes to performance-to-watt ratio, and the ARM11 processor family gives unparalleled performance while doubling battery life.”

Kerry McGuire, ARM's director of strategic software alliances, stated, “Support for big endian code enables partners to bring high quality products to market faster.”


MontaVista Linux with big endian support for the ARM1176JZ-S and ARM1176JZF-S cores is available now, says MontaVista.

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