Different microprocessors brief history of the Intel architecture design philosophy of Intel.
The 8088 is the 16-bit microprocessor that controls the standart IBM personal computers, including the original PC, the Poratble PC, and the PCjr. Almost every bit of data that enters or leaves the computer passes throught the CPU to be processed.
Inside the 8088, 14 registers provide a working area for data transfer the processing. These internal registers, forming an area 28 bytes in size, are able to temporarily store data, memory addresses, instruction pointers, and status and control flags. Throught these registers, the 8088 can access 1 MB(megabyte), or more then one million bytes, of memory.
The 8086 is used in the PS/2 models 25 and 30 (and also in many IBM PC clones). The 8086 differs from the 8088 in only one minor respect: it uses a full 16-bit data bus instead of the 8-bit bus that the 8088 uses. (The difference between 8-bit and 16-bit buses is discussed below.) Virtually anything that you read about 8086 also applies to the 8088; for programming purposes, consider them indentiical.
The 80286 is used in the PC/AT and in the PS/2 models 50 and 60/ Althought fully compatible with the 8086, th 80286 supports extra programming features that let it execute programs much more quickly than the 8086. Perhaps the most important enchancement to the 80286 is its support for multitasking.
Multitasking is the ability of CPU to perform serveral tasks at a time – such as printing a document and calculating a spreadsheet – by quickly switching its attention among the controlling programs.
The 8088 used in a PC or PC/XT can support multitasking with the help of sophisticated control software. However, an 80286 can do a much better job of multitasking because it executes programs more quickly and addresses much more memory than the 8088. Moreover, the 80286 was designed to prevent tasks from interfering with each other.
80286 can run in either of two operating modes: real mode or protected mode. In real mode, the 80286 is progammed exactly like an 8086. It can access the same 1Mb range of memory addresses as the 8086. In protected mode, however, the 80286 reserves a predetermined amount of memory for an executing program, preventing that memory from being used by any other program. This means that several programs can execute concurrently without the risk of one program accidentally changing the contents of another program`s memory area. An operating system using 80286 protected mode can allocate memory among several different tasks much more effectively than can an 8086-based operating system.
The PS/2 Model 80 uses the 80386, a faster, more powerful microprocessor than the 80286. The 80386 supports the same basic functions as the 8086 and offers the same protected-mode memory management as the 80286.
However, the 80386 offers two important advantages over its: predecessors:
The 80386 is a 32-bit microprocessor with 32-bit registers. It can perform computations and address memory 32 bits at a time instead of 16 bits at a time/
The 80386 offers more flexible memory management than the 80286 and 8086.