Dear all,
I’ve installed Gentoo on the Vision 2 Board and playing around with CFLAGS and ggc 12.2.1.
I think this are the correct one - or did anyone have different infos?
CFLAGS="-mabi=lp64d
-march=rv64imafdc_zicsr -mcpu=sifive-u74 -mtune=sifive-u74
-O2 -pipe -fomit-frame-pointer
--param l1-cache-size=32 --param l2-cache-size=2048"
I use this to build Python 3.11.1
CFLAGS="-march=rv64imafdc -mcpu=sifive-u74 -mtune=sifive-7-series"
You probably already know this, but if not you can look at what you’re getting without special tuning with:
gcc -march=native -E -v - </dev/null 2>&1 | grep cc1
The bitmap extension is available for StarFive2 CPUs.
I use -march=rv64imafdczbb0p93_zba0p93 as a compiler option.
When I tried it with a program that uses bitmaps (Shogi, Japanese Chess), there was a 5% performance improvement.
I think -march=native is not supported in RISC-V yet. Your command without grep showing this:
gcc: error: ‘-march=native’: ISA string must begin with rv32 or rv64
do we need to specify 0.93 for b extension? just asking because clang seem to refuse it, but allow just _zba_zbb.
Thank you very much for your hint 
. If we use your -march flag, then there is a noticeable improvement in my nbench benchmark (left with your march, right with the old one).
So I recommended as safe CFLAGS:
CFLAGS="-mabi=lp64d
-march=rv64imafdczbb0p93_zba0p93 -mcpu=sifive-u74 -mtune=sifive-7-series
-O2 -pipe -fomit-frame-pointer
--param l1-cache-size=32 --param l2-cache-size=2048"
you are correct.
I tried with clang first, so I gave it 0.93. Not required for gcc.
I will try to rebuild my Python with this CFLAGS, very excited to get things faster on this CPU.
What Document/Process did you follow to install Gentoo on this Board?
There is a install guide for a raspberry. you can follow this guide (Raspberry Pi/Quick Install Guide - Gentoo Wiki). Grab the modules (/lib/modules) and boot partition from starfive debian image.
You can use the risc v autobuilds: Index of /pub/Mirrors/gentoo/releases/riscv/autobuilds
If you install / compile all time, my recommendation: use a fan or a heatsink
Did you have to use the Serial Port or did it work via the HDMI port?
Hi, I tried Gentoo MUSL stage3 autobuild, but it hangs on boot without any error, the board seems to reset. Anyone tried musl one?
Normal gentoo rootfs also hangs for me on Starting Local.
Only serial and ssh access. you can possibly install the gfx binary driver but i didn’t try.
@riley10 maybe you didn’t configure your serial on the visionfive side. Normal openrc Stage 3->
/etc/inittab
s0:12345:respawn:/sbin/agetty -L 115200 ttyS0 vt102
Ok I will have to wait until I find my usb to serial adapter.
Thanks this worked to get the serial adapter working on Gentoo.
I have Gentoo running now 
Some details would be appreciated.
Gentoo runs faster on my Visionfive2 than it does on my Raspberry pi 4 running Gentoo.
I compared compile times using the genlop -t command as well as simple benchmarks like
time echo “scale=5000; 4*a(1)” | bc -l
