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knicklicht | Which variant is chosen when building with --cpu-type vexrisc but without --cpu-variant? | 06:40 |
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knicklicht | In the wiki it says "standard" is the default, but somehow I cannot get timing closure when I choose it explicitly. | 06:45 |
sensille | no idea, doesn't it say in the open while generating? | 06:47 |
sensille | btw, didn't you start with the rv901t? | 06:48 |
knicklicht | Yes, I did:-) . However, it's much easier for me to get my hands on the colorlight. The rv901t seems to be outdated. | 06:49 |
sensille | ah, i assumed you already had it | 06:50 |
sensille | i got a rv201t, it has an anlogic fpga | 06:50 |
knicklicht | For my project I don't need just one. I am currently trying to evaluate which board makes most sense for me. | 06:51 |
sensille | got my rv901t a while back for 12 euro shipped or so | 06:51 |
knicklicht | That's a great price. I got one used locally for 20€. There are some suppliers that have it in stock in china for around 17$ + taxes and shipping. | 06:52 |
knicklicht | The colorlight I can get through Ali. Since I can pay taxes and customs fees right with them, that's a lot easier for me. | 06:54 |
sensille | yeah. directly from linsn you might get a good price, but for 100+ card + shipping + customs | 06:54 |
knicklicht | Exactly, and since I need only around 15 boards that's not enough for them to even bother. | 06:56 |
sensille | did you think about making your own board? it's fun :) | 06:59 |
knicklicht | Luckily, for now I don't need the boards to evaluate my options. It's just more fun to see some stuff run on actual hardware. It's a pity that I can't get Zephyr to run. Some issue during the build process. | 07:00 |
knicklicht | Yes, but the price is just not competitive for now. | 07:00 |
knicklicht | Is it usually more busy here? I would very much like to get some input from someone using vexriscv and zephyr. | 07:04 |
sensille | not during the few weeks i'm here | 07:07 |
knicklicht | That's to bad. The project seems so well designed, but without someone answering specific questions, it's hard to get started. | 07:08 |
sensille | that was my problem, too | 07:09 |
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geertu | /4 | 12:24 |
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knicklicht41 | FYI: I got an answer in the yosys chat: You can pass --seed to nextpnr-ecp5, I wrote a script a while back to run lots of seeds in parallel and report the best https://gist.github.com/adamgreig/b040b6e3d7a7a64f613780eae6c07930 | 14:41 |
sensille | knicklicht41: do you see significant variations between seeds? | 14:48 |
knicklicht41 | Absolutely, my runs vary around 15% | 14:50 |
somlo | I generated a box plot of Fmax for a litex+Rocket design targeted at a lambdaconcept ecpix5 board. Target Fmax was 50MHz, the average result came out at about 47, went as low as 44, and eventually (after 20-30 attempts with different random seeds) passed 50 (which is when I stopped gathering data) | 15:04 |
somlo | the boxplot png itself I didn't keep, and I didn't keep the imgur.com link where I posted it either... | 15:05 |
somlo | but as gatecat mentioned in #yosys, using "--yosys-flow3" helps (a lot) toward nextpnr being able to get to a faster Fmax | 15:06 |
somlo | btw, "--yosys-flow3" is currently available in litex as a command line option for the ecp5 trellis builder | 15:07 |
knicklicht41 | Thanks somlo, where can I set "--yosys-flow3" for the trellis builder? | 15:17 |
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somlo | knicklicht41: for any board supported by litex using an ecp5 lattice fpga (see github.com/litex-hub/litex-boards), the command to build a litex SoC looks like, e.g.: "./litex-boards/litex_boards/targets/lambdaconcept_ecpix5.py --build ..." | 18:45 |
somlo | if you add "--yosys-flow3" to that command line, the build script will be generated such that flow3 will be used with yosys and abc | 18:45 |
somlo | for the "lambdaconcept_ecpix5" board, that script will be dumped to ./build/lambdaconcept_ecpix5/gateware/build_lambdaconcept_ecpix5.sh | 18:47 |
somlo | there will also be a <board_name>.ys yosys script, etc. | 18:47 |
somlo | so the litex builder will create all the magic required to pass the right arguments into yosys and abc (and nextpnr too) | 18:48 |
somlo | but look at the above mentioned shell script if you want to untangle all that and figure out what's actually being called | 18:48 |
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rtodaro[m]1 | I'm excited. It only took a few minutes to to get litex up and running on the arty a7... 🤩 | 23:17 |
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