INS8250N-B UART by National Semiconductor. Package: 40-DIP Download National Semiconductor INS8250N-A .pdf datasheet: Download National Semiconductor INS8250N-B comparison guide .pdf datasheet: Status: NOS (New Old Stock) Individually tested : YES RoHS compliant: no ***Note this is the original "slow" NMOS version of the INS8250 , and has the same flaws, and MUST only be used in genuine IBM PC or IBM PC/XT which had a BIOS workaround to cope. *** *** USE the improved "INS8250N-A" version for all later PC/XT clones which will have a clean set of BIOS . ***