The 16-bit processors: origin of x86

Introduced June 8, 1978
Clock rates:
5 MHz with 0.33 MIPS
8 MHz with 0.66 MIPS
10 MHz with 0.75 MIPS
The memory is divided into odd and even banks. It accesses both the banks simultaneuosly in order to read 16 bit of data in one clock cycle.
Bus Width 16 bits data, 20 bits address
Number of Transistors 29,000 at 3 µm
Addressable memory 1 megabyte
Up to 10X the performance of 8080 (typically lower)
Used in portable computing, and in the IBM PS/2 Model 25 and Model 30. Also used in the AT&T PC6300 / Olivetti M24, a popular IBM PC-compatible (predating the IBM PS/2 line.)
Used segment registers to access more than 64 KB of data at once, which many programmers complained made their work excessively difficult.