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XTx43/XDx33 players support the ATAPI logical interface for SSD, while the XTx44/XDx34 players support the NVMe interface. See here for more details.
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Persistent Clock
All Series 3 and 4 players have a real-time clock (RTC); however, except for the LS424 does not have a supercapacitor to keep the clock running when there is no other power source. If you power cycle a player that does not have an RTC (and an LS424 that is not connect to the Internet), day-parted presentations will not play at scheduled times.
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