Hangs on first boot
mateuszviste Your description suggests that something freezes during boot time. Not the kernel, because then it would halt much earlier. I suspect this might be either HIMEMX hanging (that's the one who prints the message about the A20 line) or COMMAND.COM (which is loaded right after HIMEMX).
Could you please try to identify which component is the culprit? To do so, easiest would be to press F5 when the kernel boots, this will skip all startup files. If your system boots with F5, then we will know for sure that the kernel and COMMAND.COM are working fine. Then you should be able to edit the file C:\CONFIG.SYS and comment or remove the line "DEVICE=C:\......HIMEMX.EXE" and see whether or not the system boots fine afterwards.
mateuszviste just in case it is confirmed that HIMEMX hangs the computer - there is an interesting read about a similar situation here: https://www.vogons.org/viewtopic.php?t=81944
The culprit was a leaky CMOS battery having damaged the A20 line...
mateuszviste issue moved to https://github.com/SvarDOS/bugz/issues/19
Sorry for a delay, shall do as soon as I get a bit of free time. Top counteract this I have a compaq portable on which only freedos/svardos manage to boot and actually work just fine, even the diagnostic disk hangs.
I have a fairly generic 486dx-66 on which SvarDos fails to boot after installation. I have played with BIOS settings for HDD (LBA/LARGE) with no effect. It hangs on line "Fast A20 method used", not sure what is happening as it works just fine on two other machines. There are no unusual ISA cards.