The ThinkPad X1 Carbon supports a 1,600MHz processor memory clock speed which is faster than most ultrabooks that are a similar age to it. Most notebook PCs of this type and age support a 133MHz processor memory clock speed. This Lenovo portable PC also supports 1 and 333MHz processor memory clock speeds.
A 1,600MHz processor memory clock speed is in fact the best supported memory clock speeds supported by processor across all notebook PCs of a similar spec and age to the ThinkPad X1 Carbon.
Across comparable types of notebook PC the worst supported memory clock speeds supported by processor is 133MHz.