This vector (0:01c0) is initialized by the BIOS to handle the periodic
interrupts generated by the Real-Time Clock; IRQ 8.

The RTC is initially programmed to generate approximately 1024 interrupts
per second.

Only AT-class and better computers use this device.

INT 1aH 06H (set user alarm)
INT 15H 8300H (set event wait interval)
INT 1cH (user timer interrupt)
INT 4aH (user alarm handler address)
- -

INT 70H: Real-Time Clock Interrupt Handler