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Memory Management Unit
A memory management unit (MMU), sometimes called paged memory management unit (PMMU), is a computer hardware unit that examines all references to computer memory, memory, and translates the memory addresses being referenced, known as virtual memory addresses, into physical addresses in main memory. In modern systems, programs generally have addresses that access the theoretical maximum memory of the computer architecture, 32 or 64 bits. The MMU maps the addresses from each program into separate areas in physical memory, which is generally much smaller than the theoretical maximum. This is possible because programs rarely use large amounts of memory at any one time. Most modern operating systems (OS) work in concert with an MMU to provide virtual memory (VM) support. The MMU tracks memory use in fixed-size blocks known as ''pages''. If a program refers to a location in a page that is not in physical memory, the MMU sends an interrupt to the operating system. The OS selects a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Microprocessor
A microprocessor is a computer processor (computing), processor for which the data processing logic and control is included on a single integrated circuit (IC), or a small number of ICs. The microprocessor contains the arithmetic, logic, and control circuitry required to perform the functions of a computer's central processing unit (CPU). The IC is capable of interpreting and executing program instructions and performing arithmetic operations. The microprocessor is a multipurpose, Clock signal, clock-driven, Processor register, register-based, digital integrated circuit that accepts binary code, binary data as input, processes it according to instruction (computing), instructions stored in its computer memory, memory, and provides results (also in binary form) as output. Microprocessors contain both combinational logic and sequential logic, sequential digital logic, and operate on numbers and symbols represented in the binary number system. The integration of a whole CPU on ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
8-bit
In computer architecture, 8-bit integers or other data units are those that are 8 bits wide (1 octet). Also, 8-bit central processing unit (CPU) and arithmetic logic unit (ALU) architectures are those that are based on registers or data buses of that size. Memory addresses (and thus address buses) for 8-bit CPUs are generally larger than 8-bit, usually 16-bit. 8-bit microcomputers are microcomputers that use 8-bit microprocessors. The term '8-bit' is also applied to the character sets that could be used on computers with 8-bit bytes, the best known being various forms of extended ASCII, including the ISO/IEC 8859 series of national character sets especially Latin 1 for English and Western European languages. The IBM System/360 introduced byte-addressable memory with 8-bit bytes, as opposed to bit-addressable or decimal digit-addressable or word-addressable memory, although its general-purpose registers were 32 bits wide, and addresses were contained in the lower 24 bits ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Intel 80286
The Intel 80286 (also marketed as the iAPX 286 and often called Intel 286) is a 16-bit microprocessor that was introduced on February 1, 1982. It was the first 8086-based CPU with separate, non- multiplexed address and data buses and also the first with memory management and wide protection abilities. It had a data size of 16 bits, and had an address width of 24 bits, which could address up to 16M of memory with a suitable operating system such as Windows compared to 1M for the 8086. The 80286 used approximately 134,000 transistors in its original nMOS ( HMOS) incarnation and, just like the contemporary 80186, it can correctly execute most software written for the earlier Intel 8086 and 8088 processors. The 80286 was employed for the IBM PC/AT, introduced in 1984, and then widely used in most PC/AT compatible computers until the early 1990s. In 1987, Intel shipped its five-millionth 80286 microprocessor. History and performance Intel's first 80286 chips were specified for ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Zilog Z280
The Zilog Z280 is a 16-bit microprocessor designed by Zilog as an enhancement of the Zilog Z80 architecture and integrating improvements from the abandoned Zilog Z800 project. First introduced in July 1987, the Z280 is considered to be a commercial failure. The Z280 was fabricated in CMOS, added a memory management unit (MMU) to expand the addressing range to 16 MB, features for multitasking and multiprocessor and coprocessor configurations, and 256 bytes of on-chip static RAM, configurable as either a cache for instructions and/or data, or as part of the ordinary address space. It has a huge number of new instructions and addressing modes giving a total of over 2000 combinations. It offers Supervisor and User operating modes, and optionally separate address spaces for instructions and data in both modes (four total possible address spaces). Its crystal or external clock signal is divided by half to drive the CPU. The CPU clock can be further divided by 1, 2, or 4 tim ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Motorola 68030
The Motorola 68030 ("''sixty-eight-oh-thirty''") is a 32-bit microprocessor in the Motorola 68000 family. It was released in 1987. The 68030 was the successor to the Motorola 68020, and was followed by the Motorola 68040. In keeping with general Motorola naming, this CPU is often referred to as the 030 (pronounced ''oh-three-oh'' or ''oh-thirty''). The 68030 is essentially a 68020 with a memory management unit (MMU) and instruction and data caches of 256 bytes each. It added a burst mode for the caches, where four longwords can be loaded into the cache in a single operation. The MMU was mostly compatible with the external 68851 that would be used with the 68020, but being internal allowed it to access memory one cycle faster than a 68020/68851 combo. The 68030 did not include a built-in floating-point unit (FPU), and was generally used with the 68881 and the faster 68882. The addition of the FPU was a major design note of the subsequent 68040. The 68030 typically increases ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Zilog Z8000
The Zilog Z8000 is a 16-bit microprocessor architecture designed by Zilog and introduced in early 1979. Two chips were initially released, differing only in the width of the address bus; the Z8001 had a 23-bit bus while the Z8002 had a 16-bit bus. Bernard Peuto designed the architecture, while Masatoshi Shima did the logic and physical implementation, assisted by a small group. In contrast to most designs of the era, the Z8000 does not use microcode, which allowed it to be implemented in only 17,500 transistors. The Z8000 is not Z80-compatible, but includes a number of design elements from it, such as combining two registers into one with twice the number of bits. The Z8000 expanded on the Z80 by allowing two 16-bit registers to operate as a 32-bit register, or four to operate as a 64-bit register. Although it saw some use in the early 1980s, it was never as popular as the Z80. It was released after the 16-bit 8086 (April 1978) and the same time as the less-expensive 8088, a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Zilog
Zilog, Inc. is an American manufacturer of microprocessors, microcontrollers, and application-specific embedded System on a chip, system-on-chip (SoC) products. The company was founded in 1974 by Federico Faggin and Ralph Ungermann, who were soon joined by Masatoshi Shima. All three had left Intel after working on the Intel 4004, 4004 and Intel 8080, 8080 microprocessors. The company's most famous product is the Zilog Z80, Z80 microprocessor, which played an important role in the evolution of early computing. Backward compatible, Software-compatible with the Intel 8080, it offered a compelling alternative due to its lower cost and increased performance, propelling it to widespread adoption in video game systems and home computers during the late 1970s and early 1980s. The name, pronounced with a long "i" (), is an acronym of ''Z integrated logic'', also thought of as "Z for the last word of Integrated Logic". History Zilog was started in California in 1974 by Federico Faggin and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Macintosh II
The Macintosh II is a personal computer designed, manufactured, and sold by Apple Computer from March 1987 to January 1990. Based on the Motorola 68020 32-bit CPU, it is the first Macintosh supporting color graphics. When introduced, a basic system with monitor and 20 MB hard drive cost . With a 13-inch color monitor and 8-bit display card, the price was about . This placed it in competition with workstations from Silicon Graphics, Sun Microsystems, and Hewlett-Packard. The Macintosh II was the first computer in the Macintosh line without a built-in display; a monitor rested on top of the case like the IBM Personal Computer and Amiga 1000. It was designed by hardware engineers Michael Dhuey (computer) and Brian Berkeley (monitor) and industrial designer Hartmut Esslinger (case). Eighteen months after its introduction, the Macintosh II was updated with a more powerful CPU and sold as the Macintosh IIx. In early 1989, the more compact Macintosh IIcx was introduced at a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Motorola 68020
The Motorola 68020 is a 32-bit microprocessor from Motorola, released in 1984. A lower-cost version was also made available, known as the 68EC020. In keeping with naming practices common to Motorola designs, the 68020 is usually referred to as the "020", pronounced "oh-two-oh" or "oh-twenty". The 020 was in the market for a relatively short time. The Motorola 68030 was announced in September 1986 and began deliveries in the summer of 1987. Priced about the same as the 020 of the time, the 030 was significantly faster and quickly replaced in 020 in almost every use. History 68000 and 68010 At the time the Motorola 68000 was designed, Motorola's design and fabrication services were outdated. Although even small companies like MOS Technology and Zilog had moved on to silicon gate depletion mode NMOS logic on ever-larger semiconductor wafer, wafers, Motorola was still using metal gates and enhancement mode and their largest fab worked on 4-inch wafers long after most lines had moved ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Motorola 68851
The Motorola 68851 is an external Memory Management Unit (MMU) which is designed to provide paged memory support for the 68020 using that processor's coprocessor interface. In theory it can be used with other processors such as the 68010 by simulating the coprocessor interface in software. Later 68K family processors such as the 68030, 68040, and 68060 have an internal MMU, and will not operate with the 68851, except possibly by simulation of the coprocessor interface. The 68851 was available as an option for the Apple Macintosh II, and was necessary to run Apple's A/UX operating system. On the classic Mac OS, Connectix Virtual was released in early 1989 and used the 68851 to provide virtual memory, which was later integrated into System 7. Very few cards for the Amiga make use of the 68851 primarily because it can only be used with a small range of processors and most Amigas and accelerator cards use a processor which either has its own MMU or cannot support an MMU. One of th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
