Chinese student designs open-source ARM processor

First came open-source software, like FreeBSD, Apache and Linux. Now, a Chinese graduate student, Shen Shengyu, is hoping to generate support for the development of open-source hardware with the release of an open-source microprocessor core design -- the primary processing circuitry of a chip -- that is compatible with the widely used ARM family of microprocessors developed by ARM Ltd.

Shen, a doctoral degree candidate at the Institute of Computer Science at China's National University of Defense Technology in Changsha, Hunan province, spent four months developing the nnARM core, which he has made available on the Internet as part of an open-source project that includes several other open-source core designs. Development of the nnARM, which is compatible with the ARM7 processor core family, was based on publicly available information obtained over the Internet, Shen said.

The ARM7 family is comprised of four 32-bit RISC processor cores, with clock speeds ranging from 50MHz to 110MHz. The chips are commonly found in mobile phone handsets, digital cameras and PDAs (personal digital assistants) running Linux or Microsoft Corp.'s Windows CE operating system.

The nnARM core was originally designed as a platform to facilitate research into low-power circuit design, Shen said. He hopes to develop a highly-accurate GPS (Global Positioning System) unit based on the nnARM core.

"My primary research interest is low-power digital circuit design, especially in instruction stream compression. So, I must have a real design that can act as the base (for my research) and ARM is the most famous core that is used in embedded environments," Shen said.

With the basic design of the nnARM core complete, Shen has turned to an online community of hardware developers to further development of the nnARM, including creating a cache and memory controller for the core. The nnARM core does not currently include support for a memory bus, which handles the transfer of data from main memory to a processor, that would allow the chip to be used in a real-world application.

"I want to make this design commercially available and raise money from it, but this will get in the way of ARM (Ltd.) so currently I only develop it as a noncommercial product," Shen said.

Shen is not the first to develop a core that is compatible with the ARM processor. Milpitas, California-based PicoTurbo Inc. is currently engaged in a patent-infringement lawsuit with ARM over whether its ARM-compatible processors violate ARM's chip architecture patents.

"We are aware of this clone," said ARM spokeswoman Michelle Spencer, adding that the company is currently looking at the nnARM architecture and plans to defend its patents legally if necessary.

While the nnARM core resembles the ARM core from the programmer's perspective, the core's structure is based on a completely different architecture, Shen said, adding that he has not been contacted by ARM officials regarding the nnARM core.

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