assembly - NASM: in/out instead of int -

when writing bootloader how make calls ports instead use of interrupts (i.e. int 10h)? there list someplace online unaware of known vectors? there place can go mapping of hardware not covered bios interrupts (i.e. pci - gpus)?

well, problem is not mapping of hardware, not bootloader in computer.

what talking writing of driver. bios manages simplest devices , uses best available methods achieve programmer wants. , programmer there api access it, x86 real mode means interrupts, simplest way of doing complete context switch.

if still want remain in real mode, there several more interrupts not aware of, can found in somehow complete ralf brown´s interrupt list.

however, pci , gpus works on high frequencies lots of data, , requires more memory , performance, can not operated on real mode. protected , long mode way go.

i8086 has mentioned in , out instructions method of accessing devices. whilst used true , devices keeps true, there many other ways of communicating hardware, e.g. memory mapping, dma or communication coprocessors. use in , out find out device´s memory lies access using memory-mapped interface. believe pci 1 of them. these interfaces not more difficult work with, more effective.

you hit wall called "lack of official , free documentation". must not disappointed this, there plenty of devices have datasheets , programmer references freely available (let's admit intel has massive documentation), although isn't going own gpu or network card.

tl;dr: should switch protected mode possible unlock new range of options, , can think of writing drivers. osdev wiki surely going great resource.