Microprocessor - 80386
Posted by Harisinh | Posted in | Posted on 4:32 AM
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The 80386 is the first popular 32-bit microprocessor. IA-32 first appeared with the 80386 processor, but the architecture was by no means completely new. IA-32’s 8-bit predecessor first appeared in the Datapoint 2200 programmable terminal, released in 1971.
It wasn’t just an evolutionary product in Intel’s growing family of microprocessors; it was revolutionary. It is a 32-bit chip that contained 275,000 transistors, could process five million instructions per second, and could run all popular operating systems, including Windows. It is also “multitasking,” meaning it could run multiple programs at the same time.
It has a pre-fetch queue length of 16 bytes. It has extensive memory management capabilities. It incorporates a sophisticated technique known as paging, in addition to the segmentation technique, for achieving virtual memory. The 80386 provided a new mode, virtual 8086 mode, in which real-mode programs could run while the processor was in protected mode. To support the concept of virtual memory to a grater extend it also has on-chip address translation unit. This, combined with a more flexible segmentation scheme and a larger addressable memory space (32 bits rather than 24, bring the total addressable memory to 4GB from 16MB and a virtual address space of 64 TB) has made 80386 protected mode the mode of choice for all modern operating systems.
Later IA-32 implementations have not made significant changes or enhancements to protected mode. IA-32 adds the extended registers EAX, ECX, EDX, EBX, EBP, ESP, ESI, EDI, EIP, and EFLAGS, as well as two additional, segment registers FS and GS. Originally all registers were special-purpose. For example, AX is originally an accumulator and could only be used as such. IA-32 lifted many of the restrictions on register usage, but some remain. For example, some instructions assume that a pointer in the EBX register is relative to the segment indexed by DS. In practice, 6 registers are available for generalpurpose use, far fewer than the number available in the ARM or IA-64 architectures.
The practical result of this register pressure is that IA-32 programs tend to make more frequent use of the stack for temporary storage. The 80386 has automatic self-test this feature is known as ‘Built-In-Self-Test’ (BIST). The BIST tests approximately one-half of the 80386 which includes the internal control ROM. After successful completion of BIST, the 80386 forms reset sequence after which it will start from the reset vector.
Microprocessor - 80386
The 80386 is the first popular 32-bit microprocessor. IA-32 first appeared with the 80386 processor, but the architecture was by no means completely new. IA-32’s 8-bit predecessor first appeared in the Datapoint 2200 programmable terminal, released in 1971.
It wasn’t just an evolutionary product in Intel’s growing family of microprocessors; it was revolutionary. It is a 32-bit chip that contained 275,000 transistors, could process five million instructions per second, and could run all popular operating systems, including Windows. It is also “multitasking,” meaning it could run multiple programs at the same time.
It has a pre-fetch queue length of 16 bytes. It has extensive memory management capabilities. It incorporates a sophisticated technique known as paging, in addition to the segmentation technique, for achieving virtual memory. The 80386 provided a new mode, virtual 8086 mode, in which real-mode programs could run while the processor was in protected mode. To support the concept of virtual memory to a grater extend it also has on-chip address translation unit. This, combined with a more flexible segmentation scheme and a larger addressable memory space (32 bits rather than 24, bring the total addressable memory to 4GB from 16MB and a virtual address space of 64 TB) has made 80386 protected mode the mode of choice for all modern operating systems.
Later IA-32 implementations have not made significant changes or enhancements to protected mode. IA-32 adds the extended registers EAX, ECX, EDX, EBX, EBP, ESP, ESI, EDI, EIP, and EFLAGS, as well as two additional, segment registers FS and GS. Originally all registers were special-purpose. For example, AX is originally an accumulator and could only be used as such. IA-32 lifted many of the restrictions on register usage, but some remain. For example, some instructions assume that a pointer in the EBX register is relative to the segment indexed by DS. In practice, 6 registers are available for generalpurpose use, far fewer than the number available in the ARM or IA-64 architectures.
The practical result of this register pressure is that IA-32 programs tend to make more frequent use of the stack for temporary storage. The 80386 has automatic self-test this feature is known as ‘Built-In-Self-Test’ (BIST). The BIST tests approximately one-half of the 80386 which includes the internal control ROM. After successful completion of BIST, the 80386 forms reset sequence after which it will start from the reset vector.
Microprocessor - 80386
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