Lexra

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Lexra did implement a 32-bit variant of the MIPS architecture. Noteworthy architectural feature was the lack of the MIPS I instructions lwl, lwr, swl and swr that optimize the handling of unaligned loads. Later the LX4580 core added hardware multithreading. Products implementing Lexra's architecture include the LX4080, LX4080P, LX4180, LX4280 and LX5280, LX8000. Today Lexra is a defunct company. Several key employees of Lexra founded the digital video core company Ultra Data Corporation located in Waltham, MA. Many other key Lexra employees, including co-founder and CEO, Charlie Cheng, now work for ASIC vendor Faraday Technology in Taiwan, Sunnyvale, CA, and Framingham, MA. Lexra co-founder and CTO Pat Hays is now vice president of engineering for MIPS Technologies, Inc. in Mountain View.

Linux support

The instructions lwl, lwr, swl and swr are covered by US patent 4,814,976. Lexra therefore choose to implement these instructions by software emulation. In the 1999 - 2002 lawsuit of MIPS Technologies, Inc. vs. Lexra, Inc. about violation of this and a second patent the court ruled that Lexra's software implementation of these instructions was violating the patent. Which obviously means Linux can't emulate them either.

Technically support for Lexra processors without adding emulation of these instructions would be possible but the question is how much sense it would make as some software may rely on it fairly heavily.

Following the lawsuit Lexra became a MIPS32 license. MIPS later acquired Lexra's IP. This resulted in the end of Lexra's former products and so at this time there also seems to be little interest in actually adding Linux support.

Realtek RTL8181

The Realtek RTL8181 is a highly integrated System-on-a-Chip with a high-performance 32-bit RISC microcontroller, two Ethernet MACs, and a WLAN controller embedded onto a single chip.

The embedded Lexra LX5280 32-bit RISC CPU runs at up to 200MHz and features separate 8KB instruction and data caches.

Realtek RTL8180

Don't confuse the RTL8181 with the RTL8180. It's just plain WLAN chip, that also happens to be the one embedded on the RTL8181.

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