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EspañolINTEL 80386
(Redirected from 80386)
The 'Intel386'[1] is a microprocessor which was used as the central processing unit (CPU) of many personal computers from 1986 until 2007. During its design phase the processor was code-named simply "P3", the third-generation processor in the x86 line, but is normally referred to as either 'i386' or just '386'. It was the first x86 processor to have a 32-bit architecture, with a basic programming model that has remained virtually unchanged for over twenty years and remains completely backward compatible. Successively newer implementations of this same architecture have become literally several hundred times faster than the original i386 chip during these years.
Designed and manufactured by Intel, the i386 processor was taped-out in October of 1985. Intel decided against producing the chip before that date, as the cost of production would have been uneconomical. Full-function chips were first delivered to customers in 1986. Motherboards for 386-based computer systems were highly elaborate and expensive to produce, but were rationalized upon the 386's mainstream adoption. The first personal computer to make use of the 386 was designed and manufactured by Compaq[1], and Andy Grove, Intel's CEO at the time, made the decision to single-source the processor, a decision that was ultimately crucial to both the processor's and Intel's success in the market.
The range of processors compatible with the 80386 is often collectively termed ''x86'' or ''the i386 architecture''; today, Intel prefers the name IA-32 however.
In May 2006 Intel announced that production of the 386 would cease at the end of September 2007. [2] Although it had long been obsolete as a personal computer CPU, Intel, and others, had continued to manufacture the chip for embedded systems, including aerospace technology.
The processor was a significant evolution in a long line of processors that stretched back to the Intel 8008. The predecessor of the 80386 was the Intel 80286, a 16-bit processor with a segment-based memory management and protection system. The 80386 added a 32-bit architecture and a paging translation unit, which made it much easier to implement operating systems
which used virtual memory.
The 80386 featured three operating modes: 'real' mode, 'protected' mode and 'virtual' mode. In the real mode, the 80386 (like the 80286) would run just as a fast 8086. The protected mode allowed the use of all the possibilities of the 286 and the protected mode extension of the 386, especially addressing up to 4 GiB of memory. Finally, the virtual 8086 mode (or ''VM86'') made it possible to run one or more virtual 8086 machines in a protected environment.
Though Intel would shortly introduce the 80486 and eventually the Intel Pentium line of processors, the support in the 386 for the 32-bit flat memory model
★ would arguably be the most important feature change until AMD released x86-64 in 2003.
''
★ Several other microprocessor architectures already had a "flat" 32-bit memory model, Motorola 68000 was launched in 1979, for instance.''
Later in the i386's production run, Intel introduced the 'i386SX', which was meant to be a low cost version of the 386 line. The SX series of chips was 32-bit internally, but had a 16-bit external data bus (in much the same way that the 8088 in the original IBM PC was a lower cost version of the 8086) and a 24 bit address bus; therefore, the processor could only address 16 MB. The original i386 was subsequently renamed the 'i386DX' to avoid confusion. Neither CPU included a math coprocessor (most motherboards included a socket for an i387), though the naming would cause some head-scratching later when the i486 came in a DX variant that did include floating-point capability (which was physically present but disabled in early i486SXs).
The 'i386SL' was introduced as an alternative processor for laptop computers. The processor offered several power management options (e.g. SMM), as well as different "sleep" modes to conserve battery power. It also contained support for an external cache of 16 to 64 KiB. The extra functions caused this variant to have over 3 times as many transistors as the i386DX. The i386SL was first available at 20 MHz clockspeed [3], with the 25 MHz model later added. [4]
An embedded version of the i386SX was produced as the 'i376'. This was later superseded by the 'i386EX', which was used in space applications such as the Hubble Space Telescope.
The first PC company to design and manufacture a PC based on the 386 was Compaq, rather than IBM, which had been dominant until that time. IBM was offered use of the processor, but relied instead on earlier processors to which it had manufacturing rights. The success of the Compaq 386 PC played an important role in creating the PC "clone" industry, and to establishing Intel (and Microsoft) as central component suppliers to it.
From a business perspective, the i386 was significant because it was the first significant microprocessor to be single-sourced – it was available only from Intel Corp. Prior to this, the difficulty of making chips and the uncertainty of reliable supply required that any mass-market semiconductor be multi-sourced, that is, made by two or more manufacturers, the second and subsequent ones manufacturing under license from the designer. Single-sourcing the i386 allowed Intel greater control over its development and substantially greater profits in later years. However, AMD introduced its compatible Am386 processor in March 1991 after overcoming legal obstacles, thus ending Intel's monopoly on 32-bit 386-compatible processors. Later Cyrix offered Cx486SLC and Cx486DLC processors, pin-compatible with 80386SX and 80386DX respectively.
1. Microprocessor Hall of Fame
★ Intel 80386 Programmer's Reference Manual 1986 (PDF)
★ Intel 80386 Programmer's Reference 1986
★ CPU-INFO: 80386, indepth processor history
★ Intel 386 manuals
The 'Intel386'[1] is a microprocessor which was used as the central processing unit (CPU) of many personal computers from 1986 until 2007. During its design phase the processor was code-named simply "P3", the third-generation processor in the x86 line, but is normally referred to as either 'i386' or just '386'. It was the first x86 processor to have a 32-bit architecture, with a basic programming model that has remained virtually unchanged for over twenty years and remains completely backward compatible. Successively newer implementations of this same architecture have become literally several hundred times faster than the original i386 chip during these years.
Designed and manufactured by Intel, the i386 processor was taped-out in October of 1985. Intel decided against producing the chip before that date, as the cost of production would have been uneconomical. Full-function chips were first delivered to customers in 1986. Motherboards for 386-based computer systems were highly elaborate and expensive to produce, but were rationalized upon the 386's mainstream adoption. The first personal computer to make use of the 386 was designed and manufactured by Compaq[1], and Andy Grove, Intel's CEO at the time, made the decision to single-source the processor, a decision that was ultimately crucial to both the processor's and Intel's success in the market.
The range of processors compatible with the 80386 is often collectively termed ''x86'' or ''the i386 architecture''; today, Intel prefers the name IA-32 however.
In May 2006 Intel announced that production of the 386 would cease at the end of September 2007. [2] Although it had long been obsolete as a personal computer CPU, Intel, and others, had continued to manufacture the chip for embedded systems, including aerospace technology.
| Contents |
| Architecture |
| i386SX |
| i386SL |
| Embedded variants |
| Business importance |
| Notes and references |
| External links |
Architecture
The processor was a significant evolution in a long line of processors that stretched back to the Intel 8008. The predecessor of the 80386 was the Intel 80286, a 16-bit processor with a segment-based memory management and protection system. The 80386 added a 32-bit architecture and a paging translation unit, which made it much easier to implement operating systems
which used virtual memory.
The 80386 featured three operating modes: 'real' mode, 'protected' mode and 'virtual' mode. In the real mode, the 80386 (like the 80286) would run just as a fast 8086. The protected mode allowed the use of all the possibilities of the 286 and the protected mode extension of the 386, especially addressing up to 4 GiB of memory. Finally, the virtual 8086 mode (or ''VM86'') made it possible to run one or more virtual 8086 machines in a protected environment.
The 386DX architecture.
Though Intel would shortly introduce the 80486 and eventually the Intel Pentium line of processors, the support in the 386 for the 32-bit flat memory model
★ would arguably be the most important feature change until AMD released x86-64 in 2003.
''
★ Several other microprocessor architectures already had a "flat" 32-bit memory model, Motorola 68000 was launched in 1979, for instance.''
i386SX
Later in the i386's production run, Intel introduced the 'i386SX', which was meant to be a low cost version of the 386 line. The SX series of chips was 32-bit internally, but had a 16-bit external data bus (in much the same way that the 8088 in the original IBM PC was a lower cost version of the 8086) and a 24 bit address bus; therefore, the processor could only address 16 MB. The original i386 was subsequently renamed the 'i386DX' to avoid confusion. Neither CPU included a math coprocessor (most motherboards included a socket for an i387), though the naming would cause some head-scratching later when the i486 came in a DX variant that did include floating-point capability (which was physically present but disabled in early i486SXs).
i386SL
The 'i386SL' was introduced as an alternative processor for laptop computers. The processor offered several power management options (e.g. SMM), as well as different "sleep" modes to conserve battery power. It also contained support for an external cache of 16 to 64 KiB. The extra functions caused this variant to have over 3 times as many transistors as the i386DX. The i386SL was first available at 20 MHz clockspeed [3], with the 25 MHz model later added. [4]
Embedded variants
An embedded version of the i386SX was produced as the 'i376'. This was later superseded by the 'i386EX', which was used in space applications such as the Hubble Space Telescope.
The AMD Am386DX-40
Business importance
The first PC company to design and manufacture a PC based on the 386 was Compaq, rather than IBM, which had been dominant until that time. IBM was offered use of the processor, but relied instead on earlier processors to which it had manufacturing rights. The success of the Compaq 386 PC played an important role in creating the PC "clone" industry, and to establishing Intel (and Microsoft) as central component suppliers to it.
From a business perspective, the i386 was significant because it was the first significant microprocessor to be single-sourced – it was available only from Intel Corp. Prior to this, the difficulty of making chips and the uncertainty of reliable supply required that any mass-market semiconductor be multi-sourced, that is, made by two or more manufacturers, the second and subsequent ones manufacturing under license from the designer. Single-sourcing the i386 allowed Intel greater control over its development and substantially greater profits in later years. However, AMD introduced its compatible Am386 processor in March 1991 after overcoming legal obstacles, thus ending Intel's monopoly on 32-bit 386-compatible processors. Later Cyrix offered Cx486SLC and Cx486DLC processors, pin-compatible with 80386SX and 80386DX respectively.
Notes and references
1. Microprocessor Hall of Fame
External links
★ Intel 80386 Programmer's Reference Manual 1986 (PDF)
★ Intel 80386 Programmer's Reference 1986
★ CPU-INFO: 80386, indepth processor history
★ Intel 386 manuals
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