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But the reason they break code compatibility or implement older versions of the architecture is that parts of the ISA are patented by MIPS. Other ISAs like Open

But the reason they break code compatibility or implement older versions of the architecture is that parts of the ISA are patented by MIPS. Other ISAs like OpenRISC, SPARC and RISC-V don't have these limitations.

alexvoica 11y ago
Yes, that is true. MIPS Technologies held patents on the MIPS ISA and most of those were transferred to Imagination when we completed the acquisition. However, many of these patents are also owned by an internationally-backed consortium which includes ARM: http://www.arm.com/about/newsroom/arm-announces-participation-in-a-consortium-to-acquire-rights-to-mips-technologies-mips-portfolio.php http://www.arm.com/about/newsroom/arm-announces-participatio... I think this announcement is particularly important because it gives students the chance to study a piece of RISC history. When I was in University studying for my Electrical Engineering degree, we were asked to clone an 8-bit MCU. While it was a useful exercise, everyone was dreaming of seeing a fully open MIPS CPU. We were taught it yes, in the Computer Architecture course, but never got a chance to see any RTL code. RTL code + slides beats slides in my book so that's why I feel this announcement is so important for me, personally - but also for universities worldwide.
- solarexplorer 11y ago
  You are right, I would haved loved this as a student too. But today there are real open source alternatives. Especially in an academic environment it is essential to be able to modify and share source code without restrictions so you can experiment and collaborate as you wish. E.g. students should be able to add custom instructions, experiment with cache architectures, build multicores, etc. All with the architecture they learned about in class.
  - alexvoica 11y ago
    So back to your point, a lot of universities teach computer architecture based on MIPS since it was defined by Patterson and Hennessy (Hennessy also co-founded MIPS Computer Systems Inc. and went into production with MIPS R2000 based on the MIPS I ISA). MIPS is a very popular architecture, having shipped in over 800 million devices last year. Now these universities that teach MIPS in their coursework have a chance to enhance the course by giving students access to the RTL too. When those students leave university, they will have the skills required to understand and work with a commercially-available CPU architecture.
    - rjsw 11y ago
      David Patterson lead the Berkeley RISC project which is the ancestor of SPARC, he didn't have anything to do with MIPS.
      - alexvoica 11y ago
        Patterson and Hennessy worked together to write http://www.amazon.com/Computer-Architecture-Fifth-Edition-Quantitative/dp/012383872X http://www.amazon.com/Computer-Architecture-Fifth-Edition-Qu... The vast majority of practical references in the book are based on the MIPS architecture (as an example of a RISC processor).
        rjsw 11y ago
        The MIPS architecture isn't defined by that book. Earlier editions used DLX for the practical examples.

alexvoica 11y ago

Yes, that is true. MIPS Technologies held patents on the MIPS ISA and most of those were transferred to Imagination when we completed the acquisition. However, many of these patents are also owned by an internationally-backed consortium which includes ARM: http://www.arm.com/about/newsroom/arm-announces-participation-in-a-consortium-to-acquire-rights-to-mips-technologies-mips-portfolio.php http://www.arm.com/about/newsroom/arm-announces-participatio... I think this announcement is particularly important because it gives students the chance to study a piece of RISC history. When I was in University studying for my Electrical Engineering degree, we were asked to clone an 8-bit MCU. While it was a useful exercise, everyone was dreaming of seeing a fully open MIPS CPU. We were taught it yes, in the Computer Architecture course, but never got a chance to see any RTL code. RTL code + slides beats slides in my book so that's why I feel this announcement is so important for me, personally - but also for universities worldwide.

solarexplorer 11y ago
You are right, I would haved loved this as a student too. But today there are real open source alternatives. Especially in an academic environment it is essential to be able to modify and share source code without restrictions so you can experiment and collaborate as you wish. E.g. students should be able to add custom instructions, experiment with cache architectures, build multicores, etc. All with the architecture they learned about in class.
- alexvoica 11y ago
  So back to your point, a lot of universities teach computer architecture based on MIPS since it was defined by Patterson and Hennessy (Hennessy also co-founded MIPS Computer Systems Inc. and went into production with MIPS R2000 based on the MIPS I ISA). MIPS is a very popular architecture, having shipped in over 800 million devices last year. Now these universities that teach MIPS in their coursework have a chance to enhance the course by giving students access to the RTL too. When those students leave university, they will have the skills required to understand and work with a commercially-available CPU architecture.
  - rjsw 11y ago
    David Patterson lead the Berkeley RISC project which is the ancestor of SPARC, he didn't have anything to do with MIPS.
    - alexvoica 11y ago
      Patterson and Hennessy worked together to write http://www.amazon.com/Computer-Architecture-Fifth-Edition-Quantitative/dp/012383872X http://www.amazon.com/Computer-Architecture-Fifth-Edition-Qu... The vast majority of practical references in the book are based on the MIPS architecture (as an example of a RISC processor).
      - rjsw 11y ago
        The MIPS architecture isn't defined by that book. Earlier editions used DLX for the practical examples.