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Intel 8008 (i8008) microprocessor family

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At a glance

8-bit microprocessor
Technology (micron):
Frequency (MHz):
0.5, 0.8
The first 8-bit microprocessor, Intel 8008 (i8008) was released 5 months after Intel 4004. The 8008 was available in two speed grades - 500 KHz and 800 KHz. Because 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

These numbers assume that the CPU uses fast memory and doesn't require wait states to access the memory. Although the effective speed in instructions per second of the 8008 microprocessor sometimes is lower than the effective speed of the 4004 CPU, overall performance of the i8008 was greater due to faster effective speed of some instructions, 8-bit architecture and more efficient instruction set. The 8008 had other advantages over the 4004:

  • 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.

One of the drawbacks of the Intel 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.

Intel 8008 microprocessor was used in Mark-8 computer, which is considered to be the first personal computer.

8008 major features and related families:

Previous Generation
Related Family
  • » 4-bit microprocessor
  • » 4 KB program memory
  • » 640 bytes data memory
  • » No interrupts
  • » 3-level deep stack
Next Generation
  • » 8-bit microprocessor
  • » Up to 4 MHz
  • » 64 KB RAM
  • » Stack in RAM
  • » 256 I/O ports
40-pin DIP

  • » 8-bit microprocessor
  • » Up to 800 KHz
  • » 16 KB memory
  • » 7-level deep stack
  • » 8 In / 24 Out ports
18-pin DIP

Die pictures:

Production microprocessors

18-pin DIP
East German clone of Intel 8008 processor
Intel C8008
0.5 MHz
18-pin ceramic DIP
Gray ceramic/gold top/gold pins
Intel C8008-1
0.8 MHz
18-pin ceramic DIP
Purple ceramic/gold top/gold pins
Intel D8008
0.5 MHz
18-pin ceramic DIP
Intel D8008-1
0.8 MHz
18-pin ceramic DIP
Microsystems International MF8008R
0.5 MHz
18-pin ceramic DIP
Gray ceramic/gold top/gold pins
Microsystems International MF8008-1R
0.8 MHz
18-pin ceramic DIP
Siemens SAB8008-1C
0.8 MHz
18-pin ceramic DIP
Purple ceramic/gold top/gold pins

There are 5 comments posted

1969 discrete logic 8008 CPU board

2014-08-06 20:15:57
Posted by: chatins

1969 3101 64-Bit Schottky Bipolar RAM on early CPU board. Board is thought to pre-date both 4004 and 8008.

1969 discrete logic 8008 CPU board

Origins of 8008 architecture

2016-02-27 00:56:09
Posted by: Henri Socha

The 8008 was a chip architecture that Computer Terminal Corp. (later renamed Datapoint Corp.) requested that intel (and Texas Instruments) build.
At the time, CTC was intel's largest customer using their 1103(?) shift register RAM for the Datapoint 3300, a glass teletype. As the 3300 had to be hardware customized at the factory for the communication protocol needed (IBM, DEC, Univac, etc. control codes), CTC intended that these differing protocols could be handled in software. The architectural design for their chip processor, ex: A, B,C, D,E, H,L registers was developed by Victor Poor and Harry Pyle on a Thanksgiving weekend in Vic's house in Fredricksburg, MD.
intel and TI said they would build the chip in a year, for about $100,000 but were unable to do so. CTC (Datapoint) requested their money back and allowed them to do what they will with their effort. intel kept on and produced what they named the 8008, a year later. TI gave up on the project.
CTC used an MSI design by Gary Asbell instead and that version was released as the Datapoint 2200, one year before the 8008 was in production. This initial Datapoint 2200 (there was a version II) was exactly binary compatible with the 8008. The 2200 was such a success for CTC they changed their name to Datapoint.

BTW: As per Harry Pyle, intel had two inputs to the architectural design, both requested to save transistors. First, the byte order was switched from big endian to little endian and second, like branch, to make subroutine call and return instructions conditional. (EX: it was a single byte instruction to conditionally return if the carry flag was set.)

Microsystems International Ltd.

2016-02-27 01:32:54
Posted by: Henri Socha

MIL was based in Kanata, Ontario, outside of Ottawa.
They were a wholly owned (joint) subsidiary of Northern Electric and Bell Northern Research.
In there facilities in Kanata, they made product all the way from growing silicon ingots, slicing out wafers, producing chips, to assembly of final product, ex: memory boards, development systems, and even a 4 function calculator (including making the LEDs).
They purchased their wafer processing technology from intel and become a second source to intel's products.
On top of this, they designed and built many chips of their own, such as a 48 bit correlator and a variant in the 4004 - 4040 family they named the MF7112.

Cycles per instruction and instruction rates are wrong.

2016-04-26 02:27:03
Posted by: Colin Douglas Howell

The cycles per instruction and instruction rates which you state for the 8008 are incorrect. The 8008 required 5 to 11 "T-states" to execute each instruction (11 T-states were required for taken jumps and subroutine calls). However, unlike in the later 8080, each T-state in the 8008 required two clock cycles, so the 8008 needed 10 to 22 clock cycles to execute each instruction. Thus the rate of instruction execution was 22,500 to 50,000 per second for the 8008 and 36,000 to 80,000 per second for the 8008-1. (Yes, this means that the 8008 actually executed instructions more slowly than the 4004.)

Still in use

2018-09-09 12:08:05
Posted by: Paul

Believe it or not where I am employed we still (2018) have equipment in service that uses this microprocessor. They are used in the control boards for SCADA remote equipment manufactured by Harris. This equipment has been in service for over 30 years.

Still in use

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