Here are some instructions for getting OpenBSD 74 running on a MilkV Mars (V1.11).

You will need:

1. SD card at least 8GB
2. An USB TTL serial adapter
3. A second machine to interact with the MilkV Mars over serial
4. An Ehternet cable and able connection to a tftp server

The original idea came from " Installing OpenBSD 7.3-current on a VisionFive2" , You can also check this instruction for references.

Steps

1. Download miniroot.img 7.4 from OpenBSD.
2. Donwload special DTB made by jh7110-starfive-visionfive-2-v1.3b.dtb and upload it to tftp server (my are 10.0.0.21)
3. Flash this miniroot.img into SD card
4. Boot the Mars and hit any key during U-Boot, now you can hit any keys during boot up

--------EEPROM INFO--------

In:    serial
Out:   serial
Err:   serial
Model: Milk-V Mars
Net:   eth0: ethernet@16030000, eth1: ethernet@16040000
switch to partitions #0, OK
mmc1 is current device
found device 1
bootmode flash device 1
** Invalid partition 3 **
Couldn't find partition mmc 1:3
Can't set block device
** Invalid partition 3 **
Couldn't find partition mmc 1:3
Can't set block device
Hit any key to stop autoboot:  0
StarFive #

5. Uboot setup ip and load DTB file by

dhcp; setenv serverip 10.0.0.21; tftpboot ${fdt_addr_r} jh7110-starfive-visionfive-2-v1.3b.dtb

load mmc 1:1 ${kernel_addr_r} efi/boot/bootriscv64.efi; bootefi ${kernel_addr_r} ${fdt_addr_r}

6. That's It! Now you can boot with OpenBSD and do install by normal process

p.s. In OpenBSD sysctl hw.perfpolicy=high to enable performance mode.