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NAS design taps low-end MIPS64 SoC

Jan 29, 2009 — by Eric Brown — from the LinuxDevices Archive — 43 views

Raza Microelectronics (RMI) announced a network-attached storage (NAS) reference design based on Linux and a new, lower-cost version of RMI's previously available XLS208 SoC. RMI's “NAS Media Server Reference Design” uses RMI's new dual-core, 750MHz XLS108 SoC, and comes with a boot loader, SDK, and “RAID-enabled” Linux 2.6 implementation.

The RMI NAS Media Server Reference Design Kit is built around a new lower-end version of RMI's XLS208 system-on-chip (SoC) that shipped last April. Like its predecessor, the XLS108 has two MIPS64 cores. However, it clocks only to 750MHz instead of 1GHz, and has a lighter mix of on-chip peripheral interfaces (more about the new chip below).

The Media Server reference design supports an unspecified amount of socketed DDR2 memory, running at up to 667MHz. It offers SATA storage interfaces, allowing up to two hard disk drives (HDDs). Supported RAID configurations include RAID 0, RAID 1, and RAID 10, says RMI. Additional interfaces (most likely USB ports) are available for external disk and other peripheral devices, and the design includes multiple gigabit Ethernet interfaces, says the company. The only other information provided on the design is the inclusion of a Mini-PCIe slot for WiFi or wireless modem support.

The RMI NAS Media Server design kit ships with an SDK, compete with an RMI boot loader and a a “RAID enabled” version of Linux 2.6.xx, says RMI. The SDK is said to offer a complete development tool kit, including an XLS-optimized GCC compiler, and a MIPS cross-compile tool chain for x86 Linux. RMI also offers an optional Linux-based XLS compiler, linker, and debugger. In addition, the SDK includes a web-based configuration GUI (evaluation only), says the company.

Typical configurations for XLS108-based products, including NAS design (middle)
(Click to enlarge)

RMI's XLS-108

The XLS108 is based on the XLS-208 SoC announced last April, but has a lower clock rate, and offers fewer PCIe lanes and gigabit Ethernet interfaces. Like the XLS208, the XLS108 is said to accelerate packet-oriented and control plane applications for SMB (small- and medium-sized businesses), says RMI. Applications are said to include security appliances, wireless access points and switches, ATCA and AMC service cards, radio controllers, network signaling products, telecom media gateways, and secured wire-line routers and switches.

The XLS108 and XLS208 fall toward the low end of the XLS family, which in turn is a scaled-down version of RMI's XLR family of multicore MIPS64-based processors. Still, both of these dual-core SoCs are more powerful than the earlier, and still shipping, single-core XLS204.

Built on TSMC's 90nm LP process, both the XLS108 and XLS208 are equipped with eight parallel processing elements that RMI calls vCPUs. These fine-grained hardware processing units are said to use single-clock, zero overhead, and context switching features.

XLS108 block diagram
(Click to enlarge)

Both XLS SoCs are equipped with Autonomous Security Acceleration Engine and Autonomous Network Acceleration Engine technologies, both of which are said to offload security and networking tasks from the CPU. XLS processors are said to be pin-compatible, including offering compatibility with both single-core and quad-core designs.

Additional features listed for both the XLS108 and XLS208 include:

  • Dual 64-bit MIPS64 cores, each with 4-way multithreading for processing of 8 threads
  • 32KB instruction and 32KB data level-1 caches
  • 512KB level-2 banked cache
  • 3 x on-chip interconnects
  • Bootable NAND flash interface
  • Dual I2C interfaces
  • Dual UART interfaces
  • 32-bit GPIO interface
  • JTAG and BIST support
  • PCMCIA interface

Differences between the XLS108 and XLS208 are as follows:

  • Clock rate — The XLS108 clocks from 500MHz to 750MHz, whereas the XLS208 ranges from 600MHz to 1GHz
  • On-chip memory controller — XLS108 supports only one 36-bit DDR2 channel while XLS208 also offers a 72-bit channel
  • Networking — XLS108 offers 3 x gigabit Ethernet MACs; XLS208 has 4 x gBe MACs
  • USB — XLS108 has 1 x USB 2.0 port instead of 2 x ports for XLS208
  • PCIe — XLS108 has 2 x PCIe lanes instead of 4 x lanes for XLS208; (XLS108 has dual PCIe 1.1 controllers supporting 2 x1 lanes, compared to XLS208's single PCIe 1.1 controller supporting 4 x1 lanes)
  • Autonomous Security Acceleration Engine — XLS108 provides up to 0.75Gbps bulk encryption/decryption instead of 1Gbps for XLS208

When RMI announced the XLS208 last year, it also introduced an “Office-in-a-Box” evaluation kit for the SoC. The kit is based on a LiTE Evaluation Board, which appears to replace RMI's earlier “ArizonaATX” line of evaluation boards for the XLS208 and the dual-core XLS408 processor. The board is said to offer a smaller form factor than the ArizonaATX, while offering DDR2 support, gigabit Ethernet, PCIe, USB, flash memory, and diagnostic interfaces.

The LiTE board also comes with BOM, schematics, and layout collateral, as well as RMI's XLS SDK, which includes reference software, tool chains, diagnostics, firmware suite, and device drivers for “open source Linux and other commercial operating systems,” according to RMI. Presumably this kit, or a similar one, will support the XLS108.

Also last year, Embedded Alley announced that RMI had joined its Silicon Vendor Partner Program (SVPP), which offers customized SDKs that vendors can freely distribute, and includes mainline Linux kernel maintenance and regression testing. In addition, Wind River ported its Carrier Grade Linux distribution, Platform for Network Equipment, Linux Edition (PNE-LE) 2.0 to RMI's XLR platform. Last April, when the announcement was made, Wind River said that XLS support was “on the roadmap.”

Stated Behrooz Abdi, president and CEO, RMI, “By bringing this optimized NAS application solution to our customers, we are able to drive high performance and cost-effective products for the low-to mid-range SMB market segments.”


No information was provided for the pricing or availability of the RMI NAS Media Server Reference Design Kit or the XLS108 processor. The XLS208, however, is priced as low as $40 in volume, and the Office-in-a-Box evaluation kit starts at $1500.

Earlier this month, RMI announced a new line of Linux-compatible, MIPS32-based SoCs for portable and low-powered multimedia devices, called the Au1300.

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