<knicklicht>
Which variant is chosen when building with --cpu-type vexrisc but without --cpu-variant?
<knicklicht>
In the wiki it says "standard" is the default, but somehow I cannot get timing closure when I choose it explicitly.
<sensille>
no idea, doesn't it say in the open while generating?
<sensille>
btw, didn't you start with the rv901t?
<knicklicht>
Yes, I did:-) . However, it's much easier for me to get my hands on the colorlight. The rv901t seems to be outdated.
<sensille>
ah, i assumed you already had it
<sensille>
i got a rv201t, it has an anlogic fpga
<knicklicht>
For my project I don't need just one. I am currently trying to evaluate which board makes most sense for me.
<sensille>
got my rv901t a while back for 12 euro shipped or so
<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.
<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.
<sensille>
yeah. directly from linsn you might get a good price, but for 100+ card + shipping + customs
<knicklicht>
Exactly, and since I need only around 15 boards that's not enough for them to even bother.
<sensille>
did you think about making your own board? it's fun :)
<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.
<knicklicht>
Yes, but the price is just not competitive for now.
<knicklicht>
Is it usually more busy here? I would very much like to get some input from someone using vexriscv and zephyr.
<sensille>
not during the few weeks i'm here
<knicklicht>
That's to bad. The project seems so well designed, but without someone answering specific questions, it's hard to get started.
<sensille>
knicklicht41: do you see significant variations between seeds?
<knicklicht41>
Absolutely, my runs vary around 15%
<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)
<somlo>
the boxplot png itself I didn't keep, and I didn't keep the imgur.com link where I posted it either...
<somlo>
but as gatecat mentioned in #yosys, using "--yosys-flow3" helps (a lot) toward nextpnr being able to get to a faster Fmax
<somlo>
btw, "--yosys-flow3" is currently available in litex as a command line option for the ecp5 trellis builder
<knicklicht41>
Thanks somlo, where can I set "--yosys-flow3" for the trellis builder?
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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 ..."
<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
<somlo>
for the "lambdaconcept_ecpix5" board, that script will be dumped to ./build/lambdaconcept_ecpix5/gateware/build_lambdaconcept_ecpix5.sh
<somlo>
there will also be a <board_name>.ys yosys script, etc.
<somlo>
so the litex builder will create all the magic required to pass the right arguments into yosys and abc (and nextpnr too)
<somlo>
but look at the above mentioned shell script if you want to untangle all that and figure out what's actually being called
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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... 🤩