Yamaha YM2413B and YMF281B are low power variants of YM2413 and YMF281 respectively. These variants also reduced the crossover distortion of the built-in DAC. A lower power consumption indicates that these variants may be made using a CMOS process. Yamaha YM2423 (OPLL-X) is another YM2413 derivative. It has the same pinout and register set as the YM2413, but a different set of built in FM patches. Yamaha YMF281 (OPLLP) is a later YM2413 derivative, possibly intended for pachinko or pachislot machines. It has the same pinout and register set as the YM2413, but a different set of built in FM patches. Yamaha FHB013 is a later YM2413 derivative. It uses a 2-metal CMOS process instead of NMOS. It has the same pinout and register set as the YM2413, but a different set of built in FM patches. It may be the same chip as the YMF281B above, as it supposedly has the same patches. It could also be directly derived from the YM2413B. UMC U3567 is a 100% software compatible chip with a slightly different pinout, requiring a pin-to-pin adapter in order to be used on a YM2413 socket. UMC UM3567 is a 100% software compatible chip, with the same pinout as the U3567 but has a slightly enhanced DAC output. It requires the same pin-to-pin adapter, but the different DAC output will also require the two pull-down resistors of the audio output pins to be removed from the mainboard. The K-663A (sometimes known as the K-663 or K-633A) is a 100% software compatible chip, possibly based on the UMC UM3567. It is used on the Korean Family Noraebang famiclone, as well as on a few arcade machines. It has the same pinout as the U3567, and has an enhanced DAC output. As with the U3567 and UM3567 chips, a pin-to-pin adapter is required to use the YM2413 sockets. See also List of sound chips Yamaha OPL References External links MSX-Music d'Osvualdo, G. (2008), Luppes, E., Martin, C., Brychkov, E. (2013) "FM-Pak without SRAM". AGE Labs, 2013-12-29. Accessed on 2013-12-31. Sound chips MSX