History of Computers - Intel's 8 Bit Microprocessor

Brian White

Ted Hoff, Stan Mazor, Hal Feeney, and Federico Faggin designed Intel's 8 bit microprocessor, known as the 8008. The 8008 was used by Dan Lancaster, a computer hobbyist,to create a predecessor to the first personal computer known as the "TV typewriter". It was used as a dumb terminal.

Overview

The 8008 was the first 8 bit microprocessor, the original designed was for use as a terminal controller for Control Terminal Corporation (CTC), the microprocessor was to be single chip version of CTC's CPU design. The 8008 was available in two different speed grades 500 KHz and 800 KHz, and it took the CPU from 5 to 8 cycles to execute each instruction, the effective rate of instruction execution was:

   * From 45,000 to 100,000 instructions per second for Intel 8008
   * From 72,000 to 160,000 instruction per second for Intel 8088-1 

The performance of the 8008 was greater than its 4004 predecessor because of faster effective speed of some instructions, 8-bit architecture and more efficient instruction set. Other advantages included:

   * The processor supported of 16 KB of memory (ROM and RAM combined).
   * The size of internal CPU stack was 7 levels in contrast to 3 level-stack for the i4004.
   * The Intel 8008 could handle interrupts. 

Unfortunately the 8008 was the absence of direct memory addressing. To access data in memory the memory address had to be stored in H and L registers, and only then the processor could indirectly access the memory. This limitation was removed in Intel 8080, which was used in the Mark-8 and considered the first personal computer.

Significance

The 8008 was used to create the first predecessor the the PC. Also the 8008 family produced 8080 which was used in the first PC, now giving us the computers we use today.

References

http://www.antiquetech.com/chips/8008.htm

http://www.cpu-world.com/CPUs/8008/index.html

http://www.computermuseum.li/Testpage/Chip-Intel8008-1972.htm