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It featured four 16-bit general registers, which could also be accessed as eight 8-bit registers, and four 16-bit index registers (including the stack pointer). The data registers were often used implicitly by instructions, complicating register allocation for temporary values. It featured 64K 8-bit I/O (or 32K 16 bit) ports and fixed vectored interrupts. Most instructions could only access one memory location, so one operand had to be a register. The result was stored in one of the operands.
There were also four segment registers that could be set from index registers. The segment registers allowed the CPU to access one megabyteA megabyte is a unit of measurement for computer storage, memory and information; while its exact definition varies, it is in theory equal to one million bytes. The symbol for megabyte is MB (note B for Byte, lowercase b would mean bit). Three definitions of memory in an odd way. Rather than just supplying missing bytes, as in most segmented processors, the 8086 shifted the segment register left 4 bits and added it to the address. As a result segments overlapped, which most people consider to have been poor design. Although this was largely acceptable (and even useful) for assembly language, where control of the segments was complete, it caused confusion in languages which make heavy use of pointers (such as CThe C Programming Language Brian Kernighan and Dennis Ritchie, the original edition that served for many years as an informal specification of the language The C programming language is a low-level standardized programming language developed in the early). It made efficient representation of pointers difficult, and made it possible to have two pointers with different values pointing to the same location. Worse, this scheme made expanding the address space to more than one megabyte difficult. Effectively, it was expanded by changing the addressing scheme in the 80286The Intel 80286 is an x86-family 16-bit microprocessor that was introduced by Intel on February 1, 1982. Initially released in 6 and 8 MHz editions, it subsequently scaled up to 20 MHz, and was widely used in IBM PC compatible computers during the mid 198.
The processor runs at clock speeds between 4.77 (in the original IBM PC) and 10 MHz.
Typical execution times in cycles (estimates):
EA: time to compute effective address, ranging from 5 to 12 cycles
The 8086 did not contain any floating pointComputer arithmetic A floating-point number is a digital representation for a number in a certain subset of the rational numbers, and is often used to approximate an arbitrary real number on a computer. In particular, it represents an integer or fixed-poi instructions, but could be connected to a mathematical coprocessors to add this capability. The Intel 8087The 8087 was the first math coprocessor designed by Intel and it was built to be paired with the Intel 8088 and 8086 microprocessors. The purpose of the 8087, the first of the x87 family, was to speed up computations on demanding applications involving fl was the standard version, but manufacturers like WeitekWeitek Corporation was a former chip-design company that originally concentrated on floating point units for a number of commercial CPU designs. During the early to mid-1980s, Weitek designs could be found powering a number of high-end designs and paralle soon offered higher performance alternatives.
The 8086 was cloned by the NEC V20The NEC V20 was a processor made by NEC that featured approximately 29,000 transistors. It was a reversed-engineered version of an Intel 8088 processor that ran at 8 to 10 megahertz. The design was more efficient then the 8088 and caused the V20 to run 30, V25 and V30 processors.