Producers of the 8031 mcu.

	ATMEL	Flash, E2, low cost and custom devices. Up to 128K+4 K flash. with. "On board" programmable devices.
	DALLAS	Enhanced speed, NV-RAM, NV-Clock, Dual Serial ports. (Nice ones!)
	INTEL	8031 and up, they invented it and still holds the lead in raw speed with the 16 bit MCS251.
	OKI	Masked variants, 85C154 with piggyback EPROM.
	PHILIPS	From 83C750 up to the XA 16 bit devices.  Many special devices with I2C-Bus and big ones with extra I/O and A/D, D/A, PWM etc.
	SIEMENS	A/D, D/A extra I/O:s and more.
SMC	SMC	COM20051 with high speed ARCNET support.
	TEMIC	CAN/VAN Interface, Low voltage versions, ROM-Security functions.
	ISSI	Fast 80C31/51 up to 40 MHz.
	TDK	Special  modem versions up to 44 MHz, Hardware CRC calculation, Bankswitching support and some other features.  Also have virtual 16C550 UART interface.
	LG	(Formerly GoldStar) "GMS90" series mcu, 80C51 compatible and OTP versions of  Atmel 89Cx051.
	WINBOND	FLASH up to 32K. AD / DA / PWM / I2C devices and extra I/O.
	Daewoo	Possibly makes MASK-ROM 8051:s. Have not found any pages on these chips.