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I heard that if you are making a PMode OS that you should reprogram the PIC. Is this true, and if so why?

Thanks in advance,
K.J.

You must program the pic in order to avoid two interrupts to be on the same number.

Under real mode, hardware interrupts are mapped in range 0->31 if I have a good memory.

Under protected mode, Intel has "reserved" this range for exception.

So you have to re-program the pic to put the hardware interrupts away from Intel's garden.

You just have to change the offset of each PIC.

ROSWELL

PS : Sorry for my english but I'm french.

Okay, so if I don't remap it then I get interrupts that don't work right? If all I want to do is just use the keyboard do I have to remap the PIC?

K.J.

under real mode you have int 0-7 and 70-78. the common thing to do is remap everything from 0-31.

check the os faq

http://www.mega-tokyo.com/os/os-faq-pics.html#remap_pic