Intel 8080

The Intel 8080 was an early microprocessor designed and manufactured by Intel. The 8-bit CPU was released in April 1974. It ran at 2 MHz, and is generally considered the first truly useful microprocessor design.

Several major manufacturers were second sources for the processor, including AMD, Mitsubishi, NatSemi, NEC, Siemens, and Texas Instruments. Also in the Eastern bloc several clones were made without licences, in countries like the Union of Soviet Socialist Republics and the Democratic Republic of Germany.

Description

Programming model

The Intel 8080 was the successor to the Intel 8008, this was because it was source compatible in assembly language because they used the same instruction set developed by Computer Terminal Corporation. With larger packaging, 40-pin DIP, the 8080 was enabled to provide a 16-bit address bus and an 8-bit data bus, allowing easy access to 64KB of memory. It had seven 8-bit registers, six of which could be combined into three 16-bit registers, a 16-bit in-memory stack pointer that replaced the 8008's internal stack, and a 16-bit program counter.

Logs

General records
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
日本語 A
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
日本語 B
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
日本語 D
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
日本語 H Δ L ε HL
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Stack Pointer and Counter Program
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
日本語 SP ̄
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
日本語 PC 日本語
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Input/output scheme

The 8080 had 256 I/O (input/output) ports that could be used by programs via dedicated I/O instructions, each of those instructions taking an I/O port address as its operand. This scheme, which used a separate address space for inputs/outputs, is now less commonly used than memory mapping for I/O devices or ports. At the time of the 8080 release, the I/O mapping scheme was seen as an advantage, as it freed up the processor's limited number of address pins for use in the memory address space. However, on most other CPU architectures, mapping the I/O ports into a common address space for memory and I/O gave a simpler instruction set, with no need for instructions at all. separate from I/O.

Support Chips

A key factor in the success of the 8080 was the wide range of support chips available, providing, among other functions, communications, counters/timers, input/output, direct memory access, and programmable interrupt controller.

• 8251. Communications controller.
• 8253. Programmable interval timer.
• 8255. Programmable interface of peripherals.
• 8257. DMA Controller.
• 8259. Programmable disruption controller.

The industrial impact

The 8080 was used in many of the early microcomputers, such as the MITS Altair 8800 and the IMSAI 8080, forming the basis for machines running the CP/M operating system. Later, in 1976, the Zilog Z80 microprocessor appeared, fully compatible with the 8080 but more capable, which would capitalize on this, with the Z80 and CP/M becoming the dominant CPU and OS combination of the period, much like x86 and the MS-DOS for the PC of the later decade, the (1980s). The first microcomputer on a single board was built on the 8080.

Shortly after the launch of the 8080, the competing design, the Motorola 6800, was introduced, and after that, the 6502, the variant of the 6800 developed by MOS Technology. At Intel, the 8080 was followed in 1976 by the more compatible and electrically elegant 8085, and later, in June 1978, by the 16-bit 8086 and in June 1979 by the 8/16-bit 8088, both of which were compatible. at the assembly language level with the 8080. The 8088 was selected by IBM for its new IBM PC to be released in 1981. In turn, through its instruction set architecture (ISA), the 8080 made a lasting impact on computer history.