INTEL 8080

General description

The Intel 8080, unveiled in 1974, represented a notable leap forward with its 8-bit architecture and approximately 6,000 transistors. Its increased clock speed and enhanced instruction set led to improved computational performance, making it a cornerstone in the evolution of microprocessors. The Intel 8080’s significance extended to its role in shaping the foundation for subsequent processors and its lasting impact on the growth of computing technology.

The 8080A is functionally and electrically compatible with the Intel® 8080

  • TTL Drive Capability
  • 2 uS (-1:1.3 µS, – 2:1.5 µS) Instruction Cycle
  • Powerful Problem Solving Instruction Set
  • 6 General Purpose Registers and an Accumulator
  • 16·Blt Program Counter for Directly Addressing up to 64K Bytes of Memory
  • 16·Blt Stack Pointer and Stack Manipulation Instructions for Rapid Switching of the Program Environment
  • Decimal, Binary, and Double Precision Arithmetic
  • Ability to Provide Priority Vectored Interrupts
  • 512 Directly Addressed 110 Ports

The Intel® 8080A is a complete 8·bit parallel central processing unit (CPU). It is fabricated on a single LSI chip using Intel’s n·channel silicon gate MOS process. This offers the user a high performance solution to control and processing applications.

The 8080A contains 6 8·bit general purpose working registers and an accumulator. The 6 general purpose registers may be addressed individually or in pairs providing both single and double precision operators. Arithmetic and logical instructions set or reset 4 testable flags. A fifth flag provides decimal arithmetic operation.

The 8080A has an external stack feature wherein any portion of memory may be used as a last in/first out stack to storelretrieve the contents of the accumulator, flags, program counter, and all of the 6 general purpose registers. The 16·bit stack pointer controls the addressing of this external stack. This stack gives the 8080A the ability to easily handle multiple level priority interrupts by rapidly storing and restoring processor status. It also provides almost unlimited subroutine nesting. This microprocessor has been designed to simplify systems design. Separate 16·line address and 8·line bidirectional data busses are used to facilitate easy interface to memory and I/O. Signals to control the interface to memory and I/O are provided directly by the 8080A. Ultimate control of the address and data busses resides with the HOLD signal. It provides the ability to suspend processor operation and force the address and data busses into a high impedance state. This permits OR·tying these busses with other controlling devices for (OMA) direct memory access or multi·processor operation.


Historical outline

The Intel 8080 was a pivotal 8-bit microprocessor that fueled early personal computers and microcomputers, shaping the microcomputer industry and paving the way for modern computing advancements.

In the early 1970s, as the demand for more powerful microprocessors grew, Intel recognized the need for advancements beyond their successful 4004 and 8008 microprocessors. Led by Federico Faggin, a design team set out to create a more capable processor.

In 1972, the team unveiled the Intel 8080, an 8-bit microprocessor with a sophisticated architecture that included 16-bit addressing, expanded memory capabilities, and an enriched instruction set. The innovative multiplexed address and data bus reduced pin requirements on the chip, and the processor boasted improved clock speed and an advanced interrupt system.

Officially released in April 1974, the Intel 8080 quickly found its place in various applications, from early personal computers to microcomputer systems. Its introduction sparked the microcomputer industry’s growth, enabling the development of more powerful and versatile machines.

The 8080’s open architecture paved the way for other companies to create compatible processors, resulting in a range of devices utilizing the 8080 architecture. This microprocessor’s influence extended to its successors, like the Intel 8085, and indirectly contributed to the emergence of the x86 architecture.

Beyond its immediate impact, the Intel 8080 played a crucial role in establishing the concept of general-purpose microprocessors. Its design principles and architectural innovations influenced the development of subsequent processors, contributing significantly to the overall growth of the computing industry.

The legacy of the Intel 8080 continued through the creation of the Intel 8086, which introduced the shift to 16-bit architecture and marked the beginning of the influential x86 processor family. The creation of the Intel 8080 marked a pivotal moment in microprocessor history, serving as a foundational stepping stone that shaped the trajectory of computing technology.

Emulation and Development Tools

The Intel MDS-800, ICE-80 and SDK-80 played essential roles in the early days of microprocessor development, enabling engineers to create software for Intel’s microprocessor architectures and contribute to the evolution of computing technology. For more detailed information, you might want to explore historical archives, documentation, or retro computing communities specializing in these technologies.
  • Intel MDS-800 (Microcomputer Development System): The Intel MDS-800 was a microcomputer development system designed to aid in the development and testing of software for Intel’s microprocessors, including the 8080 and later processors. It consisted of both hardware and software components, providing a comprehensive environment for debugging and testing microprocessor-based systems. The MDS-800 included features such as memory, I/O ports, and a console interface, enabling developers to interact with the microprocessor and their software. It played a significant role in facilitating the creation of software for Intel’s microprocessor products.
  • ICE-80 (In-Circuit Emulator for 8080): The ICE-80 was likely an In-Circuit Emulator specifically designed for the Intel 8080 microprocessor. In-Circuit Emulators are tools that allow developers to test and debug code directly on the target hardware. They offer features like real-time debugging, code tracing, and memory inspection, enhancing the development process by providing a direct view into the behavior of the microprocessor during program execution.
  • SDK-80 (Software Development Kit for 8080): The SDK-80 refers to a Software Development Kit tailored for the Intel 8080 microprocessor. A software development kit typically includes tools, libraries, documentation, and examples that aid programmers in creating software for a specific platform. The SDK-80 would have provided developers with the resources needed to write, compile, and debug software for the Intel 8080 microprocessor architecture.

Intel and Third-party Applications for the 8080 Processor

The Intel developed Single Coard Computers (SBCs) built around the Intel 8080 microprocessors. These SBCs provided a compact platform for software development and testing. There have also been many historical projects based on this processor.
  • Intel iSBC 80/10A, iSBC 8010/B and iSBC 80/20  were part of Intel’s iSBC series, encompassing SBCs centered on the Intel 8080 microprocessor. These boards integrated necessary components, furnishing a comprehensive environment for software exploration and development.
  • The Altair 8800 was introduced in 1975 by MITS and designed by Ed Roberts, is renowned as one of the earliest microcomputers. It used the Intel 8080 microprocessor, operating at 2 MHz. Sold as a kit, it marked the start of personal computing and influenced Microsoft’s beginnings with the development of Altair BASIC. The Altair’s legacy is seen in its impact on software ecosystems, industrial applications, and the evolution of personal computing culture.