Hmmmm. I can attest to qemu com ports working for my hobby OS, which does work on hardware com ports as well. For qemu, I use the com port as the primary consol

Hmmmm. I can attest to qemu com ports working for my hobby OS, which does work on hardware com ports as well. For qemu, I use the com port as the primary console. But, I just assume there's a comport at 0x3f8, I don't do detection. I don't remember if I got virtualbox com ports to work, I had a lot of trouble with virtualbox and decided it wasn't on my support list. This is output only, but if you don't have a better way to test if qemu comport works, you can run my kernel with wget https://crazierl.org/crazierl.elf qemu-system-i386 -display none -serial mon:stdio -kernel crazierl.elf You should get a bunch of useless debug output, but it came through the com1. If that's helpful, the relevant code is more or less here https://github.com/russor/crazierl/blob/4e41bfa5c5bbae078a57afa00386e7f59c9fda23/kernel_src/kernel.c#L299 https://github.com/russor/crazierl/blob/4e41bfa5c5bbae078a57... (init starts here, writing characters a smidge later on line 324)