23 Aralık 2007 Pazar
Intel 80286 cpu-info.com
The Intel's 286, introduced on February 1, 1982, (originally named 80286, and also called iAPX 286 in the programmer's manual) was an x86 16-bit microprocessor with 134,000 transistors.
It was widely used in IBM PC compatible computers during the mid 1980s to early 1990s.
After the 6 and 8 MHz initial releases, it was subsequently scaled up to 12.5 MHz. (AMD and Harris later pushed the architecture to speeds as high as 20 MHz and 25 MHz, respectively.) On average, the 80286 had a speed of about 0.21 instructions per clock.  The 6 MHz model operated at 0.9 MIPS, the 10 MHz model at 1.5 MIPS, and the 12 MHz model at 2.66 MIPs.
The 80286's performance was more than twice that of its predecessors (the Intel 8086 and Intel 8088) per clock cycle. In fact, the performance increase per clock cycle may be the largest among the generations of x86 processors. Calculation of the more complex addressing modes (such as base+index) had less clock penalty because it was performed by a special circuit in the 286; the 8086, its predecessor, had to perform effective address calculation in the general ALU, taking many cycles. Also, complex mathematical operations (such as MUL/DIV) took fewer clock cycles compared to the 8086.
Having a 24-bit address bus, The 286 was able to address up to 16 MB of RAM, in contrast to 1 MB that the 8086 could directly work with. While DOS could utilize this additional RAM (extended memory) via BIOS call (INT 15h, AH=87h), or as RAM disk, or emulation of expanded memory, cost and initial rarity of software utilizing extended memory meant that 286 computers were rarely equipped with more than a megabyte of RAM.
The 286 was designed to run multitasking applications, including communications (such as automated PBXs), real-time process control, and multi-user systems.
Manufacturers: Intel, AMD, Harris, SAB
Introduction date: February 1982
Introduction speed: 6 MHz
Maximum speed: 25 MHz
Transistor count: 134,000
Manufacturing process: 1.5 micron