Dedicated circuitry on Stratix^™ and Stratix^™ GX devices for supporting differential I/O standards at speeds up to 1 Gbps when using dynamic phase alignment (DPA). Stratix GX devices support differential I/O standards at up to 840 Mbps without using DPA. Stratix GX device source-synchronous circuitry supports the 3.3-V PCML, LVDS, LVPECL, HyperTransport^™ I/O standards.