Irq 2/9

[CoreyD]

Does anyone understand why there's a loop from IRQ 2 to IRQ 9? And also, what components connect to IRQ 2/9 -- open components like IRQ 10? Do the components connect to IRQ 2/9 at the same time since IRQ 2 basically is IRQ 9 in a sense?

 

[locki433]

originaly there were only 8 IRQ's, and when more were needed, they had to assign a certain IRQ, 2, to point to the new higher IRQ's.

 

[CoreyD]

Ok so originally there were 8 IRQs like you said:
0 - System timer
1 - Keyboard
2 - ???
3 - COM 2/4
4 - COM 1/3
5 - LPT2 (soundcard)
6 - Floppy
7 - LPT1 (printer)

But why not just add IRQ 8, 9, 10, 11, 12, 13, and 14. Then just instead of making IRQ 2 lead to IRQ 9 and adding IRQ 15 to secondary hard drive, just have IRQ 2 stay the same and just pile the new default devices over the current IRQs?

I just don't understand why we would link lower IRQs to higher IRQs....