The microprocessor i80486
Microprocessors of family х88/x86 differ from each other internal architecture, clock frequency, word length of Buss of the address and the data, but are compatible программно.
The microprocessor i8088 was анонсирован Intel in June, 1979, and in 1981 firm IBM has chosen it(him) for the first personal computer. This chip contained approximately 29 thousand transistors. Thanking he could address to 20 address lines physically area of memory in 1 Mb. Originally the microprocessor i8088 worked with frequency of 4,77 MHz and had speed about 0,33 million instructions a second (Million Instruction Per Second, MIPS), however his(its) clones designed for higher clock frequency (for example, 8 Мгц) subsequently have been developed. { IBM}
The chip 8086 which have appeared year earlier i8088, became popular basically due to computer Compaq DeskPro. These microprocessors differ word length of the external Bus of the data: 8 categories at i8088 and 16 categories at i8086. The processor i80186, found application basically in microcontrollers was issued also.
In 1982 firm Intel has issued the new microprocessor — i80286. On a crystal it has been realized about 130 thousand transistors. This chip has appeared practically simultaneously with a new computer of firm IBM — PC/AT. Alongside with increase in productivity this microprocessor could work now in two modes — real and protected. 24 address lines of the new microprocessor allowed to address in the protected mode already to 16 Mb of memory.
In 1985 firm Intel was анонсирован the first 32-bit microprocessor i80386. The new chip contained approximately 275 thousand transistors. The first computer using this microprocessor, was Compaq DeskPro 386. Completely the 32-bit architecture (32-bit registers and the 32-bit external Bus of the data) in the new microprocessor has been added with the expanded device of management of memory (Memory Management Unit, MMU). On clock frequency of 16 MHz speed of the new processor has made approximately 6 MIPS. 32 address lines of the microprocessor allowed to address 4 Gbytes of memory physically. Besides the new mode — the virtual processor (V86) has been entered. In this mode some problems, intended for i8086 could be carried out simultaneously.
Cheaper alternative to the 32-bit processor i80386 has appeared only in 1988. The new microprocessor i80386SX had internal completely 32-bit architecture, but used the 16-digit external Bus of the data and 24-digit address. Believe, that index SX (which subsequently has been replaced on DX) has taken place from word SiXteen (sixteen) according to word length of the Bus of the data.
At autumn Comdex exhibition in 1989 firm Intel for the first time announced the microprocessor 486DX which contained more than 1,2 million transistors on one crystal and has been completely compatible with processors of lines х86. The new microcircuit for the first time has united on one chip such devices, as the central processor, the mathematical coprocessor and cache - memory.
The microprocessor i80486SX, submitted in 1991, similarly to original i80486DX contains the cache - controller and cache - memory on a crystal, and the mathematical coprocessor at him(it) is blocked. Exception of expenses for testing of the coprocessor has allowed firm Intel to reduce of the price for the new microprocessor essentially. For microprocessors of family i80486 addressing of physical memory in the size of 4 Gbytes (32 categories of the address) and virtual memory in the size of 64 Tbytes is supposed.
For portable computers in 1990 firm Intel had been developed the microprocessor i80386SL which contained approximately 855 thousand transistors. The given microprocessor represents the integrated variant of the microprocessor i80386SX which base architecture is added still with several auxiliary controllers. All components necessary for construction of a portable computer, are concentrated in two microcircuits: the microprocessor i80386SL and the peripheral controller i82360SL. The new interruption named System Management Interrupt (SMI) which can be used, for example, for the first time is entered into a set i80386SL for management of power consumption.
The microcircuit i80486SL, анонсированная in 1992, unites characteristic features of two representatives of processor families Intel: i80486DX and i80386SL. On productivity the new processor does not concede i80486DX, but due to the lowered pressure(voltage) of a feed(meal) (3,3 В) and the advanced technology of management энергопотреблением (as in i80386SL) he can effectively be used in portable computers.
Microprocessors with multiplication of frequency
In 1992 firm Intel has declared creation of the second generation of the microprocessors 486 named i80486DX2 (SX2). Speed of job of their internal blocks in 2 times was higher than speed of other part of system. The opportunity of association of high efficiency of the microprocessor with internal clock frequency of 50/66 MHz and effective at cost of a system payment of 25/33 MHz thus has appeared. Simultaneously with processors DX2 processors OverDrive intended for replacement of out-of-date processors have been issued. The basic distinction between processors of series DX2 and OverDrive Intel DX2 will be, that the first are mounted on system payments even at assembly of computers, and the second can be established by users. Internal functional sites of similar microcircuits (the mathematical coprocessor, a cache, the device of management of memory, the arithmetic-logic device) use the double clock frequency, while other elements of a system payment (system and external cache - memory, auxiliary microcircuits) work with usual speed.
Multiplication of clock frequency (not only in two, but also, for example, in one and a half, two and a half or three times) since then finds wide application practically in all known processors. So, after DX2 firm Intel has issued a series of microprocessors with multiplication of frequency three times — DX4.
