What is the most direct way of addressing a graphics chip?

Question

My oldish PC has an Intel HD 420 in it.

I was wondering - we can use Assembly code to address the CPU directly, with commands like mul, add

Answer 1

If you need the ISA for Intel HD graphics, here it is. Intel provides the programmer's reference manuals for all their graphics chips here. These information can be used to create a graphics driver for Intel HD graphics, which is the most "direct" way of accessing the GPU.

Please note this is for Intel HD graphics as they are the only one who provides ISA documentation for open source driver development as I know.

Best of luck!