Friday, 2019-07-12

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promachdaveshah : should I put up a github issue for ?01:18
tpbTitle: asynchronous reset mechanism of D flip-flop in yosys - Page 1 (at
promachI am not sure that yosys-smtbmc tool is giving the right formal verification results01:18
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emeb_macon a lark, building icestorm/yosys/nextpnr on an RPi 402:42
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futarisIRCcloudemeb_mac: Should work fine. I've built it on an android termux.02:56
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emeb_macfutarisIRCcloud: seems to be working so far. Slow, but no big issues yet (about 1/2-way thru yosys now)03:01
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emeb_macwell, icestorm and yosys build OK, but nextpnr fails03:50
emeb_macnextpnr/3rdparty/qtimgui/ImGuiRenderer.h:57:5: error: ‘QOpenGLFunctions_3_2_Core’ does not name a type; did you mean ‘QOpenGLFunctionsPrivate’?03:51
emeb_macis it possible to configure the nextpnr build to leave out the GUI stuff? probably not needed on a headless system.03:55
emeb_mactry cmake w/ -DBUILD_GUI=OFF I guess04:00
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Xarkemeb_mac: I tried this recently (on a 3...) and got past here, but was blocked by a problem with mutexes at run-time IIRC.04:51
emeb_macXark: nextpnr built w/ GUI disabled. trying out tools now04:57
emeb_macyosys-abc has been spinning on a simple design for the last 10min w/o finishing.04:57
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Xarkemeb_mac: Hopefully it works.  My Pi4 should arrived soon (I for sure needed fans and swap on the Pi3...took a while too). :)04:58
Xarkemeb_mac: I did get it working for regular ice40-8K (with archnepnr vs nextpnr).04:59
Xarkemeb_mac: I think I tried maybe a month or more ago (so ancient history). :)05:00
emeb_macXark: this is my HX8K-based icestick 6502 design. It builds in a few sec on my i3 system. been running for the last 15 min or so and seems stuck at ABC: + mfs2 step05:01
emeb_macthis is a 2GB RAM version of Pi4 and top reports that it's only using 0.7% of memory.05:01
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Xarkemeb_mac: Yeah, IIRC my memory issues were compiling (1GB and I think I had a browser window open).  I think I used -j2 (-j4 was a bad idea I found).05:03
emeb_macyeah - I never use -j on systems with small memory. straight make w/o -j works fine (if slowly)05:04
Xarkemeb_mac: I also compiled RISC-V toolchain (overnight)...05:04
Xarkemeb_mac: But all those bars in htop looked so empty... :)05:05
emeb_macwell, I gave up and aborted. yosys-abc had been running on this for ~30min w/o evidence of progress. I suspect something wrong somewhere.05:19
emeb_macnow trying with a different design. it also seems hung in yosys-abc05:19
Xarkemeb_mac: Was it using CPU (or wedged on mutex)?05:24
emeb_macIt's using 100% of one CPU05:25
emeb_macand a tiny amount of RAM (0.6% in the current case)05:25
Xarkemeb_mac: I see.  Kind of a bummer.05:26
Xarkemeb_mac: Presumably Pi related?05:26
emeb_macXark: when you build these 6502 designs do you ever see this? "ABC: Warning: The network is combinational (run "fraig" or "fraig_sweep")."05:27
emeb_macI've seen that before while  building on PC but it doesn't seem to hurt anything05:27
Xarkemeb_mac: Hmm, a lot of spam, but I don't recall seeing that...05:27
* Xark greps05:28
emeb_macI see it on PC for sure but the design builds fine05:30
Xarkemeb_mac: Yeah, it is there.05:30
emeb_macand PC blows right past the yosys-abc stuff that hangs on the Pi.05:30
Xarkemeb_mac: Like I mentioned, I have gotten some designs to build and run on the Pi (but not with arachne-pnr).  I believe I got the RiscRV32 "PicoSoC" build and running (hence the RISC-V toolchain build I mentioned).05:31
XarkEr, PicoRV32 :)05:32
* Xark also remembers a lot of pauses on the Pi that were not noticeable on his PC. :)05:32
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pepijndevos_Is there a way to control fan-out in abc? It seems to want to insert buffer chips above a certain threshold.08:30
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ZirconiumXpepijndevos_: Have you made any optimisation to placement, or are you just dropping them in a grid as you go?09:41
pepijndevos_ZirconiumX, it's just droppign them in a grid. There is no placement info in the netlist at all. I think Kicad ist just doing this.09:43
pepijndevos_Which wont stop me from running the autorouter on it and watching it burn09:44
pepijndevos_Skidl is *really* slow btw, the picorv32 has not yet completed generating the netlist. the 6502 took a looong time as well.09:46
pepijndevos_I think we could look into graywolf and qrouter if we want to do bigger things than you can place by hand in Kicad.09:50
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cr1901_modern I never understood what this line meant in the README and now it's gone. What does/did it mean for yosys to synthesize "latched logic as feedback loops"?23:34
tpbTitle: Update README · YosysHQ/[email protected] · GitHub (at
sorearhave you ever seen two back to back NOR gates in a book?23:39
cr1901_modernyes I know what a latch looks like23:39
cr1901_modernI guess my question is... "in the past did yosys emulate latches using a mux that fed back the output to input with one clock cycle delay?"23:49
sorearNot a “clock cycle” delay - a combinatorial loop23:52
cr1901_modernI don't see how that's "emulating" a latch then. The whole point of a latch is that the output gets fed back to the input.23:53

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