Intel 8088

Intel 8088
Name	Intel 8088
Caption	An Intel 8088 microprocessor
Produced	From 1979 to 1990s
Designer	Intel
Common manufacturer(s)	Intel, AMD, Fujitsu, Harris Corporation
Max CPU clock rate	5 MHz to 10 MHz
Data width	8-bit
Address width	20-bit
Socket(s)	40-pin DIP
Predecessor	Intel 8085
Successor	Intel 80186, Intel 80286
Application	Desktop, embedded system

Intel 8088. The Intel 8088 is a 16-bit microprocessor designed and manufactured by Intel, introduced in 1979. It is a cost-reduced variant of the Intel 8086, featuring an 8-bit external data bus instead of a 16-bit bus. Its selection as the central processing unit for the IBM Personal Computer in 1981 cemented its place as a foundational component of the personal computer revolution.

History and background

The 8088 was developed as a follow-on to the successful Intel 8086, which debuted in 1978. Engineers at Intel, led by architects like Stephen P. Morse, sought to create a version that could use cheaper, more readily available 8-bit support chips and system components. This design strategy was aimed at reducing overall system cost while maintaining software compatibility with the more powerful 8086. The chip was formally announced in June 1979, positioned as a bridge between older 8-bit systems like those based on the Intel 8085 and the new 16-bit architecture. Its timing coincided with IBM's secretive "Project Chess," which sought to rapidly develop a competitive personal computer.

Technical specifications

The 8088 is fabricated using NMOS logic technology and initially contained approximately 29,000 transistors. Its external data bus is 8 bits wide, while its internal registers and ALU are fully 16-bit, allowing it to process 16-bit data internally. The processor features a 20-bit address bus, enabling it to directly address 1 MB of memory. Initial clock speeds were 5 MHz, with later versions such as the 8088-2 reaching 8 MHz. Manufactured in a 40-pin DIP, it required a +5V power supply. Second-source manufacturers included AMD, Fujitsu, and the Harris Corporation.

Architecture and features

The architecture of the 8088 is identical to that of the Intel 8086, employing the same instruction set and segmented memory model. It uses four 16-bit segment registers—CS, DS, SS, and ES—to generate 20-bit physical addresses. The execution unit and bus interface unit operate asynchronously, allowing for a form of primitive instruction prefetching via a 4-byte queue. Key features include capabilities for multiprocessing via the TEST pin and support for the Intel 8087 math coprocessor to accelerate floating-point calculations. Its Microcode is stored in internal ROM.

Use in the IBM PC

The pivotal moment for the 8088 was its selection by Don Estridge and the team at the IBM Entry Systems Division in Boca Raton for the original IBM Personal Computer, model 5150. This decision was driven by the chip's balance of 16-bit software capability and 8-bit system economy. The IBM PC architecture, with its IBM PC BIOS, ISA bus, and use of the Microsoft MS-DOS operating system, was built around the 8088. Its success spawned a vast ecosystem of IBM PC compatible machines from companies like Compaq, Dell, and Tandy Corporation, establishing the x86 architecture as the dominant computing platform.

Variants and successors

Several variants of the 8088 were produced. The Intel 8086 was the original full 16-bit bus version. The 8088-2 was a higher-speed 8 MHz part. An CMOS version, the 80C88, was produced for low-power applications. The chip was directly succeeded by the Intel 80186 and Intel 80286, which offered integrated peripherals and protected mode operation, respectively. Other contemporary but incompatible competitors included the Motorola 68000 and the Zilog Z8000.

Impact and legacy

The Intel 8088's role in the IBM PC made it the central processor for the dawn of widespread personal computing, profoundly impacting business, education, and home technology. It established the x86 architecture's overwhelming market dominance, a lineage extending through the Intel 80386, Pentium, and modern Core processors. The ecosystem it enabled led to the rise of dominant software companies like Microsoft and Lotus Software. The 8088 is celebrated as a milestone in the history of computing, marking the transition from proprietary systems to an open, standardized hardware platform.

Category:Intel microprocessors Category:1979 introductions Category:IBM PC compatibles Category:x86 microprocessors