This paper proposes a prototype downlink I/F employing a tapered-BW daisy-chained topology enabled by a proposed SCM2 technique to exploit the low throughput of NAND I/O, which allows a NAND controller to handle 32 NAND PKGs on a single I/F channel. The fabricated I/F achieved 12.8 Gb/s with BER of 10−¹² while consuming 252.1 mW for a TX and 375.7 mW for four RXs. The FoM is 409.6 PKG·Gb/s.