Hello Dan! I assume you mean a Dell XPS L501x.

Resolution above 1366x768 requires a double channel video cable (8 more physical wires)
Most laptop that shipped with an LCD resolution of 1366x768 are equipped with a "lighter" single channel cable. Laptops that are equipped with a single channel cable would require a video cable replacement for a resolution upgrade. A full featured cable will usually have markings of "FHD" or "FullHD", while a single channel (lighter) cable can be marked as "HD". Since your laptop was originally manufactured for a variety of LCD options - there is a good chance that your cable is already full-featured; alternatively you should have no problem sourcing a FHD cable from Dell (or used from other sources) for your LCD upgrade.
(For laptops that were only released with a 1366x768 screen finding a FHD cable is nearly impossible)

Regards,

Ellis

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