8086 Processor
A Historical Background
The Microprocessor Age
Ø The world’s first microprocessor, the Intel 4004, was a 4-bit microprocessor– programmable controller on a chip.
Ø It addressed a mere 4096, 4-bit-wide memory locations. (A bit is a binary digit with a value of one or zero. A 4-bit-wide memory location is often called a nibble.)
Ø The 4004 instruction set contained only 45 instructions.
Ø It was fabricated with the P-channel MOSFET technology that only allowed it to execute instructions at the slow rate of 50 KIPs (kilo-instructions per second).
Ø The 4-bit microprocessor debuted in early video game systems and small microprocessorbased control systems.
Ø The main problems with this early microprocessor were its speed, word width, and memory size.
Ø The Intel then released the 4040 microprocessor, a 4-bit microprocessor an updated version of the earlier 4004.
Ø In 1971, Intel Corporation released the 8008—an extended 8-bit version of the 4004 microprocessor.
Ø The 8008 addressed an expanded memory size (16K bytes) and contained additional instructions (a total of 48) that provided an opportunity for its application in more advanced systems.
Ø About six months later Intel released the 8080 microprocessor,
The 8085 Microprocessor
Ø In 1977, Intel Corporation introduced an updated version of the 8080—the 8085.
Ø The 8085 was to be the last 8-bit, general-purpose microprocessor developed by Intel.
Ø The 8085 executed software at an even higher speed. An addition that took 2.0 μs (500,000 instructions per second on the 8080) required only 1.3 μs (769,230 instructions per second) on the 8085.
Ø The main advantages of the 8085 were its internal clock generator, internal system controller, and higher clock frequency.
The Modern Microprocessor
Ø In 1978, Intel released the 8086 microprocessor; a year or so later, it released the 8088.
Ø Both devices are 16-bit microprocessors, which executed instructions in as little as 400ns (2.5 MIPs, or 2.5 millions of instructions per second).
Ø The 8086 and 8088 addressed 1M byte of memory, which was 16 times more memory than the 8085.
Ø This higher execution speed and larger memory size allowed the 8086 and 8088 to replace smaller minicomputers in many applications.
Ø One other feature found in the 8086/8088 was a small 4- or 6-byte instruction cache or queue that pre-fetched a few instructions before they were executed.
Ø In addition, the number of instructions increased from 45 on the 4004, to 246 on the 8085, to well over 20,000 variations on the 8086 and 8088 microprocessors.
Ø These microprocessors are called CISC (complex instruction set computers) because of the number and complexity of instructions.
Ø Soon, even the 1M-byte memory system proved limiting for large databases and other applications.
Ø This led Intel to introduce the 80286 microprocessor, an updated 8086, in 1983.
Ø Besides providing higher clocking speeds, the 80386 included a memory management unit that allowed memory resources to be allocated and managed by the operating system.
Ø The 80386 included hardware circuitry for memory management and memory assignment, which improved its efficiency and reduced software overhead
The 80486 Microprocessor
Ø In 1989, Intel released the 80486 microprocessor, which incorporated an 80386-like microprocessor, an 80387-like numeric coprocessor, and an 8K-byte cache memory system into one integrated package
Ø The internal structure of the 80486 was modified from the 80386 so that about half of its instructions executed in one clock instead of two clocks.
Ø The 80486 was available in a 50 MHz version, about half of the instructions executed in 25 ns (50 MIPs).
The Pentium Microprocessor
Ø The Pentium, introduced in 1993, was similar to the 80386 and 80486 microprocessors.
Ø The two introductory versions of the Pentium operated with a clocking frequency of 60 MHz and 66 MHz, and a speed of 110 MIPs, with a higher-frequency 100 MHz one and one-half clocked version that operated at 150 MIPs.
Ø The double-clocked Pentium, operating at 120 MHz and 133 MHz, was also available, as were higher-speed versions.
Ø The cache size was increased to 16K bytes from the 8K cache found in the basic version which allowed a program that transfers a large amount of memory data to still benefit from a cache. The memory system contained up to 4G bytes, with the data bus width increased from the 32 bits found in the 80386 and 80486 to a full 64 bits.
Ø The data bus transfer speed was either 60 MHz or 66 MHz, depending on the version of the Pentium. Pentium Pro Processor
The Pentium Pro processor
Ø contains 21 million transistors, integer units, as well as a floating-point unit to increase the performance of most software.
Ø The basic clock frequency was 150 MHz and 166 MHz in the initial offering made available in late 1995.
Ø In addition to the internal 16K level-one (L1) cache (8K for data and 8K for instructions) the Pentium Pro processor also contains a 256K level-two (L2) cache.
Pentium II and Pentium Xeon Microprocessors
Ø The Pentium II microprocessor (released in 1997) represents a new direction for Intel. Instead of being an integrated circuit as with prior versions of the microprocessor, Intel has placed the Pentium II on a small circuit board.
Ø The main reason for the change is that the L2 cache found on the main circuit board of the Pentium does not operate at the system bus speed of 60 MHz or 66 MHz.
Ø In mid-1998 Intel announced a new version of the Pentium II called the Xeon6 which was specifically designed for high-end workstation and server applications.
Ø The main difference between the Pentium II and the Pentium II Xeon is that the Xeon is available with a L1 cache size of 32K bytes and a L2 cache size of either 512K, 1M, or 2M bytes.
Pentium III Microprocessor
Ø The Pentium III microprocessor uses a faster core than the Pentium II, but it is still a Pentium Pro processor.
Ø It is also available in the slot 1 version mounted on a plastic cartridge and a socket 370 version called a flip-chip.
Ø Pentium III is available with clock frequencies of up to 1 GHz.
Pentium 4 and Core2 Microprocessors
Ø The Pentium 4 microprocessor was first made available in late 2000. The next version of the Pentium is called the Core2 by Intel.
Ø The Pentium 4 and Core2, like the Pentium Pro through the Pentium III, use the Intel P6 architecture. The Pentium 4 is available in speeds to 3.2 GHz and faster and the chip sets that support the Pentium 4 use the RAMBUS or DDR memory technologies in place of once standard SDRAM technology.
Ø The Core2 is available at speeds of up to 3 GHz. These higher microprocessor speeds are made available by an improvement in the size of the internal note that Intel has changed the level 1 cache size from 32K to 8K bytes and most recently to 64K.
Pentium 4 and Core2, 64-bit and Multiple Core Microprocessors
Ø Intel has included new modifications to the Pentium 4 and Core2 that include a 64-bit core and multiple cores.
Ø The 64-bit modification allows the microprocessor to address more than 4G bytes of memory through a wider 64-bit address.
Ø Currently, 40 address pins in these newer versions allow up to 1T (terabytes) of memory to be accessed.
Ø The 64-bit machine also allows 64-bit integer arithmetic, but this is much less important than the ability to address more memory.
Ø The biggest advancement in the technology is the inclusion of multiple cores. Each core executes a separate task in a program, which increases the speed of execution if a program is written to take advantage of the multiple cores.
Ø Programs that do this are called multithreaded applications. Currently, Intel manufactures dual and quad core versions, but in the future the number of cores will likely increase to eight or even sixteen.
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