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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 the fe ...
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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 (computing), 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 Motorola 68851, 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 Motorola 68881, 68881 and the faster Motorola 68882, 68882. The addition of the FPU was a major d ...
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68k Architecture
The Motorola 68000 series (also known as 680x0, m68000, m68k, or 68k) is a family of 32-bit computing, 32-bit complex instruction set computer (CISC) microprocessors. During the 1980s and early 1990s, they were popular in personal computers and workstations and were the primary competitors of Intel's x86 microprocessors. They were best known as the processors used in the early Apple Macintosh, the Sharp X68000, the Commodore Amiga, the Sinclair QL, the Atari ST, the Sega Genesis (Mega Drive), the CP System, Capcom System I (Arcade), the AT&T UNIX PC, the Tandy TRS-80 Model II#Model 16B and Tandy 6000, Model 16/16B/6000, the Sun Microsystems Sun-1, Sun-2 and Sun-3, the NeXT Computer, NeXTcube, NeXTstation, and NeXTcube Turbo, the Texas Instruments TI-89/TI-92 calculators, the Palm Pilot (all models running Palm OS 4.x or earlier) and the Space Shuttle. Although no modern desktop computers are based on processors in the 680x0 series, derivative processors are still widely used in e ...
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68020
The Motorola 68020 ("''sixty-eight-oh-twenty''", "''sixty-eight-oh-two-oh''" or "''six-eight-oh-two-oh''") 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 Technologies and Zilog had moved on to silicon gate depletion mode NMOS logic on ever-larger wafers, Motorola was still using metal gates and enhancement mode and thei ...
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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 around . 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 price simi ...
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Amiga
Amiga is a family of personal computers introduced by Commodore in 1985. The original model is one of a number of mid-1980s computers with 16- or 32-bit processors, 256 KB or more of RAM, mouse-based GUIs, and significantly improved graphics and audio compared to previous 8-bit systems. This includes the Atari ST—released earlier the same year—as well as the Macintosh and Acorn Archimedes. Based on the Motorola 68000 microprocessor, the Amiga differs from its contemporaries through the inclusion of custom hardware to accelerate graphics and sound, including sprite (computer graphics), sprites and a blitter, and a pre-emptive multitasking operating system called AmigaOS. The Amiga 1000 was released in July 1985, but production problems kept it from becoming widely available until early 1986. The best-selling model, the Amiga 500, was introduced in 1987 along with the more expandable Amiga 2000. The Amiga 3000 was introduced in 1990, followed by the Amiga 500 Plus, and Am ...
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Amiga 2500
The Amiga 2000, or A2000, is a personal computer released by Commodore in March 1987. It was introduced as a "big box" expandable variant of the Amiga 1000 but quickly redesigned to share most of its electronic components with the contemporary Amiga 500 for cost reduction. Expansion capabilities include two 3.5" drive bays (one of which is used by the included floppy drive) and one 5.25" bay that could be used by a 5.25" floppy drive (for IBM PC compatibility), a hard drive, or CD-ROM once they became available. The Amiga 2000 is the first Amiga model that allows expansion cards to be added internally. SCSI host adapters, memory cards, CPU cards, network cards, graphics cards, serial port cards, and PC compatibility cards were available, and multiple expansions can be used simultaneously without requiring an expansion cage like the Amiga 1000 does. Not only does the Amiga 2000 include five Zorro II card slots, the motherboard also has four PC ISA slots, two of which are inline wit ...
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Memory Management Unit
A memory management unit (MMU), sometimes called paged memory management unit (PMMU), is a computer hardware unit having all memory references passed through itself, primarily performing the translation of virtual memory addresses to physical addresses. An MMU effectively performs virtual memory management, handling at the same time memory protection, cache control, bus arbitration and, in simpler computer architectures (especially 8-bit systems), bank switching. Overview Modern MMUs typically divide the virtual address space (the range of addresses used by the processor) into pages, each having a size which is a power of 2, usually a few kilobytes, but they may be much larger. The bottom bits of the address (the offset within a page) are left unchanged. The upper address bits are the virtual page numbers. Page table entries Most MMUs use an in-memory table of items called a "page table", containing one "page table entry" (PTE) per page, to map virtual page numbers to ph ...
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Classic Mac OS
Mac OS (originally System Software; retronym: Classic Mac OS) is the series of operating systems developed for the Macintosh family of personal computers by Apple Computer from 1984 to 2001, starting with System 1 and ending with Mac OS 9. The Macintosh operating system is credited with having popularized the graphical user interface concept. It was included with every Macintosh that was sold during the era in which it was developed, and many updates to the system software were done in conjunction with the introduction of new Macintosh systems. Apple released the Macintosh 128K, original Macintosh on January 24, 1984. The System 1, first version of the system software, which had no official name, was partially based on the Lisa OS, which Apple previously released for the Apple Lisa, Lisa computer in 1983. As part of an agreement allowing Xerox to buy Share (finance), shares in Apple at a favorable price, it also used concepts from the Xerox PARC Xerox Alto, Alto computer, which ...
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Motorola 68451
The MC68451 is a Motorola (now Freescale) Memory Management Unit (MMU), which was primarily used in conjunction with the Motorola MC68010 microprocessor. The MC68451 supported a 16 MB address space and provided a MC68000 or a MC68010 with support for memory management and protection of memory against unauthorized access. The block size was variable, so it was usually used for segment-based memory management. It supported the mapping of up to 32 memory segments or pages of a variable size from logical to physical addresses. To allow more segments or pages, the simultaneous use of multiple MC68451 MMUs was supported In combination with a MC68010, the MC68451 permitted the realization of virtual memory. With the earlier MC68000, this was not possible due to the way the MC68000 treated memory access errors, i.e. processor state could not always be properly restored after a page fault; two MC68000s would be required, with the main CPU pausing when it got a memory access error, and ...
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Motorola 68851 Die
Motorola, Inc. () was an American multinational telecommunications company based in Schaumburg, Illinois, United States. After having lost $4.3 billion from 2007 to 2009, the company split into two independent public companies, Motorola Mobility and Motorola Solutions on January 4, 2011. Motorola Solutions is the legal successor to Motorola, Inc., as the reorganization was structured with Motorola Mobility being spun off. Motorola Mobility was acquired by Lenovo in 2014. Motorola designed and sold wireless network equipment such as cellular transmission base stations and signal amplifiers. Motorola's home and broadcast network products included set-top boxes, digital video recorders, and network equipment used to enable video broadcasting, computer telephony, and high-definition television. Its business and government customers consisted mainly of wireless voice and broadband systems (used to build private networks), and, public safety communications systems like Astro an ...
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68010
The Motorola MC68010 processor is a 16/32-bit microprocessor from Motorola, released in 1982 as the successor to the Motorola 68000. It fixes several small flaws in the 68000, and adds a few features. The 68010 is pin-compatible with the 68000, but is not 100% software compatible. Some of the differences were: * The MOVE from SR instruction is now privileged (it may only be executed in supervisor mode). This means that the 68010 meets Popek and Goldberg virtualization requirements. Because the 68000 offers an unprivileged MOVE from SR, it does not meet them. * The MOVE from CCR instruction was added to partially compensate for the removal of the user-mode MOVE from SR. * It can recover from bus faults, and re-run the last instruction, allowing it to implement virtual memory. * The exception stack frame is different. * It introduced a 22-bit Vector Base Register (VBR) that holds A 1:10of the 1 KiB-aligned base address for the exception vector table. The 68000 vector table was al ...
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68040
The Motorola 68040 ("''sixty-eight-oh-forty''") is a 32-bit microprocessor in the Motorola 68000 series, released in 1990. It is the successor to the 68030 and is followed by the 68060, skipping the 68050. In keeping with general Motorola naming, the 68040 is often referred to as simply the '040 (pronounced ''oh-four-oh'' or ''oh-forty''). The 68040 was the first 680x0 family member with an on-chip Floating-Point Unit (FPU). It thus included all of the functionality that previously required external chips, namely the FPU and Memory Management Unit (MMU), which was added in the 68030. It also had split instruction and data caches of 4 kilobytes each. It was fully pipelined, with six stages. Versions of the 68040 were created for specific market segments, including the 68LC040, which removed the FPU, and the 68EC040, which removed both the FPU and MMU. Motorola had intended the EC variant for embedded use, but embedded processors during the 68040's time did not need the pow ...
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