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74LS139

The 7400 series of chips perform transistor-transistor logic. From Wikipedia, the 74LS series is "Low-power Schottky. Implemented using the same technology as 74S but with reduced power consumption and switching speed, due to larger resistors. Typical 10 ns gate delay, remarkable (for the time) 2 mW dissipation, 4.75–5.25 V." In layman's terms, on SNES PCBs, these chips link together ROM and RAM chips. The 74LS139 chips can be found on PCBs with SRAM.

SN74LS139N
Chip type: 74LS139
Manufacturer: Texas Instruments
Date format: xYWWxxxxx
Variables: Full part #, Date code
SN74LS139AN
Chip type: 74LS139
Manufacturer: Texas Instruments
Date format: YWWxxxx
Variables: Full part #, Date code
MB74LS139
Chip type: 74LS139
Manufacturer: Fujitsu
Date format: YYWW xxx
Variables: Date code
HD74LS139P
Chip type: 74LS139
Manufacturer: Hitachi
Date format: YMW x
Variables: Date code

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