Documenting a bit in interrupts

ableos/src/arch/x86_64/interrupts.rs

@@ -177,11 +177,17 @@ pub fn init_idt() {
     IDT.load();
 }
 
+/// https://wiki.osdev.org/Pit
+/// 
 const PIT_MAX_FREQ: u32 = 1193180;
 
 pub fn set_pit_frequency(pit: u16, freq: u32) {
+    // Dividing the maximum frequency by the desired frequency
+    // gives roughly what the maximum value for the timer
+    // counter should be to run at the desired frequency.
     let ret = (PIT_MAX_FREQ / freq).try_into();
 
+    // Type-bounded counter maximum.
     let divisor: u16 = match ret {
         Ok(div) => div,
         Err(err) => {