fast PLL Definition

A feature available in supported device ( Arria^® series, and Stratix^® IV) families that employs a phase-locked loop (PLL). The fast PLL is optimized for high-speed serializer/deserializer circuitry, but can be used for logic that is independent of high-speed I/O interfaces.

You can enable the fast PLL circuitry with the altpll megafunction.