High-speed serial data transceiver circuitry on a programmable logic device (“PLD”) includes some channels that are able to operate at data rates up to a first, relatively low maximum data rate, and other channels that are able to operate at data rates up to a second, relatively high maximum data rate. The relatively low-speed channels are served by relatively low-speed phase locked loop (“PLL”) circuitry, and have other circuit components that are typically needed for handling data that is transmitted at relatively low data rates. The relatively high-speed channels are served by relatively high-speed PLLs, and have other circuit components that are typically needed for handling data that is transmitted at relatively high data rates.