[SOLVED] Why does it matter to have some delays after I/O reading?

[QB114514]

I have following a tutorial to make my own OS. In the tutorial I see that there are some delays after each in instruction like this:

Code: Select all

in dx, al
jmp $+2
jmp $+2
jmp $+2
; Something

I'm confused with why does it matter. Can you help me know it?

[Octocontrabass]

I have following a tutorial to make my own OS.

Careful. Most tutorials have bugs.

In the tutorial I see that there are some delays after each in instruction like this:

It's not really after the IN instruction, it's between the IN instruction and the next I/O instruction.

I'm confused with why does it matter. Can you help me know it?

It probably doesn't matter. Delays between I/O instructions are usually only needed on extremely old PCs, and the "jmp $+2" instruction only adds a delay on ancient (i386 and older) CPUs.

[QB114514]

So is it means it's not required on the most of modern PCs?

[Octocontrabass]

Correct.

[QB114514]

Thanks.

[QB114514]

tl;dr it does NOT matter on the most platforms