Author here. Your guess is right. A lot of hardware has migrated from using I/O ports to memory-mapped I/O, and instead of fixed I/O addresses ACPI or a simila

Author here. Your guess is right. A lot of hardware has migrated from using I/O ports to memory-mapped I/O, and instead of fixed I/O addresses ACPI or a similar mechanism provides the OS with the directory of memory addresses to talk to. For example, instead of PS/2 keyboard/mouse at I/O ports 0x0060-0x0064, ACPI provides the OS with the memory address to talk to a USB controller, and the USB controller does not use I/O ports at all. Have a look at a list of the most common I/O ports: https://wiki.osdev.org/I/O_Ports#The_list https://wiki.osdev.org/I/O_Ports#The_list Most of this hardware is gone. The easiest way to see them at all is to boot a VM in QEMU and specifically ask for these ancient devices to be present.