The Pentium uses an interrupt system for dealing with external memory.
There is a single Interrupt Request line connected to the dcontrol unit (INTR).
There is a single Interrupt Acknowledge line connected to the control unit (INTA).
These lines connect to an interrupt arbiter which is independent from the CPU.
The arbiters decide which device has more priority and which device connects to the CPU.
With one arbiter the Pentium can house up to 8 external devices.
With nesting the arbiters the Pentium can house up to 64 external devices.