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Comment by bjackman | Hacker News Reader

I believe the Xilinx tools are actually free of cost. Still, though, open source FPGA tools are desperately needed.

edit: even if they just opened up the bitfile format. I believe it's a similar situation as GPU instructions sets though: managers saying "no because patents".

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I recently wrote a place and route tool for Lattice iCE40 FPGAs [0]. The bitstream was reverse engineered by Clifford Wolf and others as part of the IceStorm project [1]. We're using Yosys [2] for Verilog synthesis, also written by Clifford.

[0] https://github.com/cseed/arachne-pnr

[1] http://www.clifford.at/icestorm/

[2] http://www.clifford.at/yosys/

Wow, that is pretty awesome. I didn't expect this to have arrived that quickly.

Does it support user constraints on relative placement (and routing)? Self-timed logic, such as NULL Convention Logic [1], doesn't fit well with the synchronous FPGA paradigm, but can be implement on those if the feedback loops are tightly controlled [2]. I'd like to play with that :)

[1] http://en.wikipedia.org/wiki/Asynchronous_circuit

    http://www.amazon.com/Designing-Asynchronous-Circuits-Convention-Synthesis/dp/1598299816

[2] http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=543867...

Whoa, I had no idea you could do async circuits on an FPGA (although I can't get to [2] right now, the site is under maintenance). Right now, I only support IO constraints. The IceStorm project hasn't documented the timing model yet but it is in pipeline. Is it possible to do what you want with vendor tools? Anyways, email me and we can chat about what you'd need.

Xilinx tools are only free for certain chips and feature sets. If you want tools like ChipScope (which more than pays for itself) or to use any Vertex chips you need to buy their software.

For their lower end chips (All the Spartan series, the larger of the 6 series are still quite useful) they straight up announced an end of development on the main toolchain (ISE) with no plans for support on their newer one.

Opening up the spec alone is not ideal, and its not just for the patents. Hardware validation of a software spec is expensive. Today they don't need to do that. They can simply change the software to work around broken hardware and nobody needs to know.

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