8250	The first UART in this line. It doesn't contain any scratch registers. 8250A is a modernized version of 8250, its bus operating speed is very fast.
8250A	The bus operating speed of this UART is greater than 8250's. It is used in the same way as 16450 in the sphere of software.
8250B	Very similar to that of the 8250 UART.
16450	Used in AT's (Improved bus speed over 8250's). Works stable at 38.4KBPS. Widespread today.
16550	This line is the first generation of buffered UART. This line has 16-byte buffer, however it doesn't work and is replaced with the 16550A.
16550A	This line is the most widespread UART version used for high-speed connection of modems with 14.4KBPS and 28.8KBPS rates. They made sure the FIFO buffers worked on this UART.
16650	New generation of UART. Contains 32 bytes of FIFO, programmed register of X-On/X-Off characters and supports power management.
16750	Produced by Texas Instruments. Contains 64-byte FIFO buffer.