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86-493: The Motorola 68000 (sometimes shortened to Motorola 68k or m68k and usually pronounced "sixty-eight-thousand") is a 16/32-bit complex instruction set computer (CISC) microprocessor , introduced in 1979 by Motorola Semiconductor Products Sector. The design implements a 32-bit instruction set , with 32-bit registers and a 16-bit internal data bus . The address bus is 24 bits and does not use memory segmentation , which made it easier to program for. Internally, it uses

172-417: A 16-bit data arithmetic logic unit (ALU) and two more 16-bit ALUs used mostly for addresses, and has a 16-bit external data bus . For this reason, Motorola termed it a 16/32-bit processor. As one of the first widely available processors with a 32-bit instruction set, large unsegmented address space, and relatively high speed for the era, the 68k was a popular design through the 1980s. It was widely used in

258-520: A PDP-8 , an Intel 80386 , an Intel 4004 , a Motorola 68000 , a System z mainframe, a Burroughs B5000 , a VAX , a Zilog Z80000 , and a MOS Technology 6502 all vary widely in the number, sizes, and formats of instructions, the number, types, and sizes of registers, and the available data types. Some have hardware support for operations like scanning for a substring, arbitrary-precision BCD arithmetic, or transcendental functions , while others have only 8-bit addition and subtraction. But they are all in

344-525: A 16-bit status register. The upper 8 bits is the system byte, and modification of it is privileged. The lower 8 bits is the user byte, also known as the condition code register (CCR), and modification of it is not privileged. The 68000 comparison, arithmetic, and logic operations modify condition codes to record their results for use by later conditional jumps. The condition code bits are "carry" (C), "overflow" (V), "zero" (Z), "negative" (N) and "extend" (X). The "extend" (X) flag deserves special mention, because it

430-411: A 64-pin package. This became known as the "Texas Cockroach". By the mid-1970s, Motorola's MOS design techniques had become less advanced than their competition, and their fabrication lines at times struggled with low yields . By the late-1970s, the company had entered a technology exchange program with Hitachi , dramatically improving their production capabilities. As part of this, a new fab named MOS-8

516-464: A dual 68000 CPU configuration, and systems with a triple 68000 CPU configuration also exist (such as Galaxy Force and others based on the Sega Y Board), along with a quad 68000 CPU configuration, which has been used by Jaleco (one 68000 for sound has a lower clock rate compared to the other 68000 CPUs) for games such as Big Run and Cisco Heat ; another, fifth 68000 (at a different clock rate than

602-492: A fairly simple superscalar design to be located after the (fairly complex) decoders (and buffers), giving, so to speak, the best of both worlds in many respects. This technique is also used in IBM z196 and later z/Architecture microprocessors. The terms CISC and RISC have become less meaningful with the continued evolution of both CISC and RISC designs and implementations. The first highly (or tightly) pipelined x86 implementations,

688-491: A higher-numbered interrupt can always interrupt a lower-numbered interrupt. In the status register, a privileged instruction allows setting the current minimum interrupt level, blocking lower or equal priority interrupts. For example, if the interrupt level in the status register is set to 3, higher levels from 4 to 7 can cause an exception. Level 7 is a level triggered non-maskable interrupt (NMI). Level 1 can be interrupted by any higher level. Level 0 means no interrupt. The level

774-420: A larger subset of instructions in a pipelined (overlapping) fashion, and facilitates more advanced extraction of parallelism out of the code stream, for even higher performance. Contrary to popular simplifications (present also in some academic texts,) not all CISCs are microcoded or have "complex" instructions. As CISC became a catch-all term meaning anything that's not a load–store (RISC) architecture, it's not

860-436: A logically flat 32-bit address space , while accessing only a 24-bit physical address space. Motorola's intent with the internal 32-bit address space was forward compatibility, making it feasible to write 68000 software that would take full advantage of later 32-bit implementations of the 68000 instruction set. However, this did not prevent programmers from writing forward incompatible software. "24-bit" software that discarded

946-412: A minimum instruction size of 16 bits. Many instructions and addressing modes are longer to include more address or mode bits. The CPU, and later the whole family, implements two levels of privilege. User mode gives access to everything except privileged instructions such as interrupt level controls. Supervisor privilege gives access to everything. An interrupt always becomes supervisory. The supervisor bit

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1032-567: A new generation of personal computers with graphical user interfaces , including the Macintosh 128K , Amiga , Atari ST , and X68000 . The Sega Genesis/Mega Drive console, released in 1988, is also powered by the 68000. Later processors in the Motorola 68000 series , beginning with the Motorola 68020 , use full 32-bit ALUs and have full 32-bit address and data buses, speeding up 32-bit operations and allowing 32-bit addressing, rather than

1118-449: A processor which in many ways is reminiscent in structure to very early CPU designs. In the early 1970s, this gave rise to ideas to return to simpler processor designs in order to make it more feasible to cope without ( then relatively large and expensive) ROM tables and/or PLA structures for sequencing and/or decoding. An early (retroactively) RISC- labeled processor ( IBM 801  – IBM 's Watson Research Center, mid-1970s)

1204-406: A reorder buffer, is a RISC, while Minimal CISC has 8 instructions, but is clearly a CISC because it combines memory access and computation in the same instructions. Million instructions per second Instructions per second ( IPS ) is a measure of a computer 's processor speed. For complex instruction set computers (CISCs), different instructions take different amounts of time, so

1290-415: A sequence of simpler instructions. One reason for this was that architects ( microcode writers) sometimes "over-designed" assembly language instructions, including features that could not be implemented efficiently on the basic hardware available. There could, for instance, be "side effects" (above conventional flags), such as the setting of a register or memory location that was perhaps seldom used; if this

1376-615: Is also the CPU of the Sega Pico , a young childrens' educational game console. The multi-processor Atari Jaguar console from 1993 used a 68000 as a support chip, although, due to familiarity, some developers used it as the primary processor. The 1994 Sega Saturn console used the 68000 as a sound co-processor. In October 1995, the 68000 made it into a handheld game console , Sega's Genesis Nomad , as its CPU. Certain arcade games (such as Steel Gunner and others based on Namco System 2 ) use

1462-771: Is called the MC68HC000, while Hitachi's is the HD68HC000. The 68HC000 offers speeds of 8–20 MHz. Except for using CMOS circuitry, it behaved identically to the HMOS MC68000, but the change to CMOS greatly reduced its power consumption. The original HMOS MC68000 consumed around 1.35  watts at an ambient temperature of 25  °C , regardless of clock speed, while the MC68HC000 consumed only 0.13 watts at 8 MHz and 0.38 watts at 20 MHz. (Unlike CMOS circuits, HMOS still draws power when idle, so power consumption varies little with clock rate.) Apple selected

1548-404: Is commonly used in association with a metric prefix (k, M, G, T, P, or E) to form kilo instructions per second ( kIPS ), mega instructions per second ( MIPS ), giga instructions per second ( GIPS ) and so on. Formerly TIPS was used occasionally for "thousand IPS". IPS can be calculated using this equation: However, the instructions/cycle measurement depends on the instruction sequence,

1634-412: Is rarely used today, as most current microprocessors can execute at least a million instructions per second. Gibson divided computer instructions into 12 classes, based on the IBM 704 architecture, adding a 13th class to account for indexing time. Weights were primarily based on analysis of seven scientific programs run on the 704, with a small contribution from some IBM 650 programs. The overall score

1720-409: Is separate from the carry flag . This permits the extra bit from arithmetic, logic, and shift operations to be separated from the carry multiprecision arithmetic . The designers attempted to make the assembly language orthogonal . That is, instructions are divided into operations and address modes , and almost all address modes are available for almost all instructions. There are 56 instructions and

1806-457: Is stored in the status register, and is visible to user programs. An advantage of this system is that the supervisor level has a separate stack pointer. This permits a multitasking system to use very small stacks for tasks, because the designers do not have to allocate the memory required to hold the stack frames of a maximum stack-up of interrupts. The CPU recognizes seven interrupt levels. Levels 1 through 5 are strictly prioritized. That is,

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1892-412: Is stored in the status register, and is visible to user-level programs. Hardware interrupts are signalled to the CPU using three inputs that encode the highest pending interrupt priority. A separate encoder is usually required to encode the interrupts, though for systems that do not require more than three hardware interrupts it is possible to connect the interrupt signals directly to the encoded inputs at

1978-474: The 68020 and 88000 projects. Several other companies were second-source manufacturers of the HMOS 68000. These included Hitachi (HD68000), who shrank the feature size to 2.7 μm for their 12.5 MHz version, Mostek (MK68000), Rockwell (R68000), Signetics (SCN68000), Thomson / SGS-Thomson (originally EF68000 and later TS68000), and Toshiba (TMP68000). Toshiba was also a second-source maker of

2064-538: The 680x0 , CPU32 , and Coldfire families, were also still in production. More recently, with the Sendai fab closure, all 68HC000, 68020, 68030, and 68882 parts have been discontinued, leaving only the 68SEC000 in production. Since being succeeded by "true" 32-bit microprocessors, the 68000 is used as the core of many microcontrollers . In 1989, Motorola introduced the MC68302 communications processor. IBM considered

2150-484: The Macintosh moved from the 6809 to the 68k. The average price eventually reached $ 14.76. In 1982, the 68000 received a minor update to its instruction set architecture (ISA) to support virtual memory and to conform to the Popek and Goldberg virtualization requirements . The updated chip is called the 68010 . It also adds a new "loop mode" which speeds up small loops, and increases overall performance by about 10% at

2236-654: The Microchip Technology PIC has been labeled RISC in some circles and CISC in others. Before the RISC philosophy became prominent, many computer architects tried to bridge the so-called semantic gap , i.e., to design instruction sets that directly support high-level programming constructs such as procedure calls, loop control, and complex addressing modes , allowing data structure and array accesses to be combined into single instructions. Instructions are also typically highly encoded in order to further enhance

2322-509: The Motorola 68000 Educational Computer Board , a single-board computer for educational and training purposes which in addition to the 68000 itself contained memory, I/O devices, programmable timer and wire-wrap area for custom circuitry. The board remained in use in US colleges as a tool for learning assembly programming until the early 1990s. At its introduction, the 68000 was first used in high-priced systems, including multiuser microcomputers like

2408-813: The PDP-11 and VAX architectures, and many others. Well known microprocessors and microcontrollers that have also been labeled CISC in many academic publications include the Motorola 6800 , 6809 and 68000 families; the Intel 8080 , iAPX 432 , x86 and 8051 families; the Zilog Z80 , Z8 and Z8000 families; the National Semiconductor NS320xx family; the MOS Technology 6502 family; and others. Some designs have been regarded as borderline cases by some writers. For instance,

2494-402: The PDP-11 , the most popular minicomputer design of the era. At the time, a key concept in minis was the concept of an orthogonal instruction set , in which every operation was allowed to work on any sort of data. To feed the correct data into the internal units, MACSS made extensive use of microcode , essentially small programs in read only memory that gathered up the required data, performed

2580-858: The Palm PDAs and the Handspring Visor used the DragonBall , a derivative of the 68000. AlphaSmart used the DragonBall family in later versions of its portable word processors. Texas Instruments used the 68000 in its high-end graphing calculators, the TI-89 and TI-92 series and Voyage 200 . A modified version of the 68000 formed the basis of the IBM XT/370 hardware emulator of the System 370 processor. Video game manufacturers used

2666-571: The WICAT 150, early Alpha Microsystems computers, Sage II / IV , Tandy 6000 / TRS-80 Model 16 , and Fortune 32:16 ; single-user workstations such as Hewlett-Packard 's HP 9000 Series 200 systems, the first Apollo/Domain systems, Sun Microsystems ' Sun-1 , and the Corvus Concept ; and graphics terminals like Digital Equipment Corporation 's VAXstation 100 and Silicon Graphics ' IRIS 1000 and 1200. Unix systems rapidly moved to

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2752-511: The 1970s, analysis of high-level languages indicated compilers produced some complex corresponding machine language. It was determined that new instructions could improve performance. Some instructions were added that were never intended to be used in assembly language but fit well with compiled high-level languages. Compilers were updated to take advantage of these instructions. The benefits of semantically rich instructions with compact encodings can be seen in modern processors as well, particularly in

2838-439: The 1990s in low-end printers. The 68000 was successful in the field of industrial control systems. Among the systems benefited from having a 68000 or derivative as their microprocessor were families of programmable logic controllers (PLCs) manufactured by Allen-Bradley , Texas Instruments and subsequently, following the acquisition of that division of TI, by Siemens . Users of such systems do not accept product obsolescence at

2924-469: The 24-bit addressing of the 68000 and 68010 or the 31-bit addressing of the Motorola 68012 . The original 68k is generally software forward-compatible with the rest of the line despite being limited to a 16-bit wide external bus. After 45 years in production , the 68000 architecture is still in use. Motorola's first widely produced microprocessor was the 6800 , introduced in early 1974 and available in quantity late that year. The company set itself

3010-546: The 486 designs from Intel , AMD , Cyrix , and IBM , supported every instruction that their predecessors did, but achieved maximum efficiency only on a fairly simple x86 subset that was only a little more than a typical RISC instruction set (i.e., without typical RISC load–store limits). The Intel P5 Pentium generation was a superscalar version of these principles. However, modern x86 processors also (typically) decode and split instructions into dynamic sequences of internally buffered micro-operations , which helps execute

3096-583: The 6800 dimming, but still cash-flush from the engine control sales, in late 1976 Colin Crook, Operations Manager, began considering how to successfully win future sales. They were aware that Intel was working on a 16-bit extension of their 8080 series, which would emerge as the Intel 8086 , and had heard rumors of a 16-bit Zilog Z80 , which became the Z8000 . These would use new design techniques that would eliminate

3182-450: The 68000 (including the 9400/9400A) can also perform fast Fourier transform functions on a waveform. The 683XX microcontrollers, based on the 68000 architecture, are used in networking and telecom equipment, television set-top boxes, laboratory and medical instruments, and even handheld calculators. The MC68302 and its derivatives have been used in many telecom products from Cisco, 3com, Ascend, Marconi, Cyclades and others. Past models of

3268-528: The 68000 as the backbone of many arcade games and home game consoles : Atari's Food Fight , from 1982, was one of the first 68000-based arcade games. Others included Sega 's System 16 , Capcom 's CP System and CPS-2 , and SNK 's Neo Geo . By the late 1980s, the 68000 was inexpensive enough to power home game consoles, such as Sega's Genesis console, and also the Sega CD attachment for it (a Sega CD system has three CPUs, two of them 68000s.) The 68000

3354-459: The 68000 for the IBM PC but chose the Intel 8088 ; however, IBM Instruments briefly sold the 68000-based IBM System 9000 laboratory computer systems. The 68k instruction set is particularly well suited to implement Unix, and the 68000 and its successors became the dominant CPUs for Unix-based workstations including Sun workstations and Apollo/Domain workstations. In 1981, Motorola introduced

3440-500: The 68000 itself had to succeed despite initially adopting a metal-gate design. Though the point about playing catch-up is clear, this could not have been an entirely accurate summary because Motorola's 1976 datasheets, predating the inception of the MACCS project, denote the majority of its 6800 family in silicon-gate. Indeed, Gunter's own 1979 article introducing the 68000 highlighted it as a silicon-gate depletion-mode HMOS design. Whatever

3526-472: The 68000 to respond quickly to interrupts (even in the worst case where all 8 data registers D0–D7 and 7 address registers A0–A6 needed to be saved, 15 registers in total), and yet large enough to make most calculations fast, because they could be done entirely within the processor without keeping any partial results in memory. (Note that an exception routine in supervisor mode can also save the user stack pointer A7, which would total 8 address registers. However,

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3612-684: The 68HC000 for use in the Macintosh Portable . Motorola replaced the MC68008 with the MC68HC001 in 1990. This chip resembles the 68HC000 in most respects, but its data bus can operate in either 16-bit or 8-bit mode, depending on the value of an input pin at reset. Thus, like the 68008, it can be used in systems with cheaper 8-bit memories. The later evolution of the 68000 focused on more modern embedded control applications and on-chip peripherals. The 68EC000 chip and SCM68000 core remove

3698-528: The CISC category . because they have "load-operate" instructions that load and/or store memory contents within the same instructions that perform the actual calculations. For instance, the PDP-8, having only 8 fixed-length instructions and no microcode at all, is a CISC because of how the instructions work, PowerPC, which has over 230 instructions (more than some VAXes), and complex internals like register renaming and

3784-533: The CMOS 68HC000 (TMP68HC000). Encrypted variants of the 68000, being the Hitachi FD1089 and FD1094, store decryption keys for opcodes and opcode data in battery-backed memory and were used in certain Sega arcade systems including System 16 to prevent piracy and illegal bootleg games. The 68HC000, the first CMOS version of the 68000, was designed by Hitachi and jointly introduced in 1985. Motorola's version

3870-550: The Imagen Imprint-10 were controlled by external boards equipped with the 68000. The first HP LaserJet , introduced in 1984, came with a built-in 8 MHz 68000. Other printer manufacturers adopted the 68000, including Apple with its introduction of the LaserWriter in 1985, the first PostScript laser printer. The 68000 continued to be widely used in printers throughout the rest of the 1980s, persisting well into

3956-631: The M6800 peripheral bus, and exclude the MOVE from SR instruction from user mode programs, making the 68EC000 and 68SEC000 the only 68000 CPUs not 100% object code compatible with previous 68000 CPUs when run in User Mode. When run in Supervisor Mode, there is no difference. In 1996, Motorola updated the standalone core with fully static circuitry, drawing only 2  μW in low-power mode, calling it

4042-735: The MC68000, the fastest version of the original HMOS chip, was not produced until the late 1980s. By the start of 1981, the 68k was winning orders in the high end, and Gunter began to approach Apple to win their business. At that time, the 68k sold for about $ 125 in quantity. In meetings with Steve Jobs , Jobs talked about using the 68k in the Apple Lisa , but stated "the real future is in this product that I'm personally doing. If you want this business, you got to commit that you'll sell it for $ 15." Motorola countered by offering to sell it at $ 55 at first, then step down to $ 35, and so on. Jobs agreed, and

4128-515: The MC68SEC000. Motorola ceased production of the HMOS MC68000, as well as the MC68008, MC68010, MC68330, and MC68340 in on June 1, 1996, but its spin-off company Freescale Semiconductor was still producing the MC68HC000, MC68HC001, MC68EC000, and MC68SEC000, as well as the MC68302 and MC68306 microcontrollers and later versions of the DragonBall family. The 68000's architectural descendants,

4214-438: The aim of higher throughput at lower cost and also allowed high-level language constructs to be expressed by fewer instructions, it was observed that this was not always the case. For instance, low-end versions of complex architectures (i.e. using less hardware) could lead to situations where it was possible to improve performance by not using a complex instruction (such as a procedure call or enter instruction) but instead using

4300-440: The basic structure of RISC processors. The CDC 6600 supercomputer, first delivered in 1965, has also been retroactively described as RISC. It had a load–store architecture which allowed up to five loads and two stores to be in progress simultaneously under programmer control. It also had multiple function units which could operate at the same time. In a more modern context, the complex variable-length encoding used by some of

4386-621: The code density. The compact nature of such instruction sets results in smaller program sizes and fewer main memory accesses (which were often slow), which at the time (early 1960s and onwards) resulted in a tremendous saving on the cost of computer memory and disc storage, as well as faster execution. It also meant good programming productivity even in assembly language , as high level languages such as Fortran or Algol were not always available or appropriate. Indeed, microprocessors in this category are sometimes still programmed in assembly language for certain types of critical applications. In

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4472-526: The code, although this is strongly mediated by the fast cache structures used in modern designs, as well as by other measures. Due to inherently compact and semantically rich instructions, the average amount of work performed per machine code unit (i.e. per byte or bit) is higher for a CISC than a RISC processor, which may give it a significant advantage in a modern cache-based implementation. Transistors for logic, PLAs, and microcode are no longer scarce resources; only large high-speed cache memories are limited by

4558-846: The cost of more software complexity. The interrupt controller can be as simple as a 74LS148 priority encoder, or may be part of a very large-scale integration (VLSI) peripheral chip such as the MC68901 Multi-Function Peripheral (used in the Atari ST range of computers and X68000 ), which also provides a UART , timer, and parallel I/O. Complex instruction set computer Examples of CISC architectures include complex mainframe computers to simplistic microcontrollers where memory load and store operations are not separated from arithmetic instructions. Specific instruction set architectures that have been retroactively labeled CISC are System/360 through z/Architecture ,

4644-625: The data and external factors. Before standard benchmarks were available, average speed rating of computers was based on calculations for a mix of instructions with the results given in kilo instructions per second (kIPS). The most famous was the Gibson Mix , produced by Jack Clark Gibson of IBM for scientific applications in 1959. Other ratings, such as the ADP mix which does not include floating point operations, were produced for commercial applications. The thousand instructions per second (kIPS) unit

4730-689: The degree of Motorola's process and manufacturing deficits in the early days, the team was undeterred and would not compromise in its pursuit of a microprocessor with industry-leading performance. Formally introduced in September 1979, initial samples were released in February 1980, with production chips available over the counter in November. Initial speed grades were 4, 6, and 8  MHz . 10 MHz chips became available during 1981, and 12.5 MHz chips by June 1982. The 16.67 MHz "12F" version of

4816-415: The dual stack pointer (A7 and supervisor-mode A7') design of the 68000 makes this normally unnecessary, except when a task switch is performed in a multitasking system.) Having the two types of registers allows one 32-bit address and one 16-bit data calculation to take place at the same time. This results in reduced instruction execution time as addresses and data can be processed in parallel. The 68000 has

4902-533: The goal of selling 25,000 units by September 1976, a goal they did meet. Although a capable design, it was eclipsed by more powerful designs, such as the Zilog Z80 , and less expensive designs, such as the MOS Technology 6502 . By late 1976, the sales book was flat and the division was only saved by a project for General Motors that turned into a huge product line for engine control and other tasks. By

4988-419: The high-performance segment where caches are a central component (as opposed to most embedded systems ). This is because these fast, but complex and expensive, memories are inherently limited in size, making compact code beneficial. Of course, the fundamental reason they are needed is that main memories (i.e., dynamic RAM today) remain slow compared to a (high-performance) CPU core. While many designs achieved

5074-462: The maximum number of transistors today. Although complex, the transistor count of CISC decoders do not grow exponentially like the total number of transistors per processor (the majority typically used for caches). Together with better tools and enhanced technologies, this has led to new implementations of highly encoded and variable-length designs without load–store limitations (i.e. non-RISC). This governs re-implementations of older architectures such as

5160-548: The mid-1980s. For this reason, MIPS has become not a measure of instruction execution speed, but task performance speed compared to a reference. In the late 1970s, minicomputer performance was compared using VAX MIPS , where computers were measured on a task and their performance rated against the VAX-11/780 that was marketed as a 1 MIPS machine. (The measure was also known as the VAX Unit of Performance or VUP .) This

5246-543: The more capable later generations of the 68k line, which remained popular in that market throughout the 1980s. By the mid-1980s, falling production cost made the 68000 viable for use in personal computers starting with the Apple Lisa and Macintosh , and followed by the Amiga , Atari ST , and X68000 . The Sinclair QL microcomputer, along with its derivatives, such as the ICL One Per Desk business terminal,

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5332-572: The most powerful processor on the market. Another 16-bit would not do, their design would have to be bigger, and that meant having some 32-bit features. Crook had decided on this approach by the end of 1976. Crook formed the Motorola Advanced Computer System on Silicon (MACSS) project to build the design and hired Tom Gunter to be its principal architect. Gunter began forming his team in January 1977. The performance goal

5418-444: The number of instructions, nor the complexity of the implementation or of the instructions, that define CISC, but that arithmetic instructions also perform memory accesses. Compared to a small 8-bit CISC processor, a RISC floating-point instruction is complex. CISC does not even need to have complex addressing modes; 32- or 64-bit RISC processors may well have more complex addressing modes than small 8-bit CISC processors. A PDP-10 ,

5504-475: The operations and wrote out the results. MACSS was among the first to use this technique in a microprocessor. There was a large amount of support hardware for the 6800 that would remain useful, things like UARTs and similar interfacing systems. For this reason, the new design retained a bus protocol compatibility mode for existing 6800 peripheral devices. A chip with 32 data and 32 addressing pins would require 64 pins, plus more for power and other features. At

5590-526: The other 68000 CPUs) was used in the Jaleco arcade game Wild Pilot for input/output (I/O) processing. The 68000 has a 24-bit external address bus and two byte-select signals "replaced" A0. These 24 lines can therefore address 16 MB of physical memory with byte resolution. Address storage and computation uses 32 bits internally; however, the 8 high-order address bits are ignored due to the physical lack of device pins. This allows it to run software written for

5676-456: The part of the processor designer in cases where a simpler, but (typically) slower, solution based on decode tables and/or microcode sequencing is not appropriate. At a time when transistors and other components were a limited resource, this also left fewer components and less opportunity for other types of performance optimizations. The circuitry that performs the actions defined by the microcode in many (but not all) CISC processors is, in itself,

5762-404: The problems seen in earlier 16-bit systems. Motorola knew that if they launched a product similar to the 8086, within 10% of its capabilities, Intel would outperform them in the market. In order to compete, they set themselves the goal of being two times as powerful at the same cost, or one-half the cost with the same performance. Crook decided that they would attack the high-end of the market with

5848-470: The processor may be capable of executing multiple independent instructions simultaneously. MIPS can be useful when comparing performance between processors made with similar architecture (e.g. Microchip branded microcontrollers), but they are difficult to compare between differing CPU architectures . This led to the term "Meaningless Indicator of Processor Speed," or less commonly, "Meaningless Indices of Performance," being popular amongst technical people by

5934-491: The programming language used. The Whetstone Report has a table showing MWIPS speeds of PCs via early interpreters and compilers up to modern languages. The first PC compiler was for BASIC (1982) when a 4.8 MHz 8088/87 CPU obtained 0.01 MWIPS. Results on a 2.4 GHz Intel Core 2 Duo (1 CPU 2007) vary from 9.7 MWIPS using BASIC Interpreter, 59 MWIPS via BASIC Compiler, 347 MWIPS using 1987 Fortran, 1,534 MWIPS through HTML/Java to 2,403 MWIPS using

6020-417: The release of the 1989 Mac IIci. The 68000 family stores multi-byte integers in memory in big-endian order. The CPU has eight 32-bit general-purpose data registers (D0-D7), and eight address registers (A0-A7). The last address register is the stack pointer , and assemblers accept the label SP as equivalent to A7. This was a good number of registers at the time in many ways. It was small enough to allow

6106-423: The same clock speeds. A further extended version, which exposes 31 bits of the address bus, was also produced in small quantities as the 68012 . To support lower-cost systems and control applications with smaller memory sizes, Motorola introduced the 8-bit compatible MC68008 , also in 1982. This is a 68000 with an 8-bit data bus and a smaller (20-bit) address bus. After 1982, Motorola devoted more attention to

6192-609: The same rate as domestic users, and it is entirely likely that despite having been installed over 20 years ago, many 68000-based controllers will continue in reliable service well into the 21st century. In a number of digital oscilloscopes from the 80s, the 68000 has been used as a waveform display processor; some models including the LeCroy 9400/9400A also use the 68000 as a waveform math processor (including addition, subtraction, multiplication, and division of two waveforms/references/waveform memories), and some digital oscilloscopes using

6278-566: The time the 6800 was introduced, a small number of 16-bit designs had come to market. These were generally modeled on minicomputer platforms like the Data General Nova or PDP-8 . Based on the semiconductor manufacturing processes of the era, these were often multi-chip solutions like the National Semiconductor IMP-16 , or the single-chip PACE that had issues with speed. With the sales prospects for

6364-421: The time, 64-pin dual inline package (DIP)s were "large, heavy-cost" systems and "just terrible", making that the largest they could consider. To make it fit, Crook selected a hybrid design, with a 32-bit instruction set architecture (ISA) but 16-bit components implementing it, like the arithmetic logic unit (ALU). The external interface was reduced to 16 data pins and 24 for addresses, allowing it all to fit in

6450-414: The typical CISC architectures makes it complicated, but still feasible, to build a superscalar implementation of a CISC programming model directly ; the in-order superscalar original Pentium and the out-of-order superscalar Cyrix 6x86 are well-known examples of this. The frequent memory accesses for operands of a typical CISC machine may limit the instruction-level parallelism that can be extracted from

6536-470: The ubiquitous x86 (see below) as well as new designs for microcontrollers for embedded systems , and similar uses. The superscalar complexity in the case of modern x86 was solved by converting instructions into one or more micro-operations and dynamically issuing those micro-operations, i.e. indirect and dynamic superscalar execution; the Pentium Pro and AMD K5 are early examples of this. It allows

6622-464: The upper address byte, or used it for purposes other than addressing, could fail on 32-bit 68000 implementations. For example, early (pre-7.0) versions of Apple's Mac OS used the high byte of memory-block master pointers to hold flags such as locked and purgeable . Later versions of the OS moved the flags to a nearby location, and Apple began shipping computers which had " 32-bit clean " ROMs beginning with

6708-731: The value measured depends on the instruction mix; even for comparing processors in the same family the IPS measurement can be problematic. Many reported IPS values have represented "peak" execution rates on artificial instruction sequences with few branches and no cache contention , whereas realistic workloads typically lead to significantly lower IPS values. Memory hierarchy also greatly affects processor performance, an issue barely considered in IPS calculations. Because of these problems, synthetic benchmarks such as Dhrystone are now generally used to estimate computer performance in commonly used applications, and raw IPS has fallen into disuse. The term

6794-458: Was a tightly pipelined simple machine originally intended to be used as an internal microcode kernel, or engine, in CISC designs, but also became the processor that introduced the RISC idea to a somewhat larger audience. Simplicity and regularity also in the visible instruction set would make it easier to implement overlapping processor stages ( pipelining ) at the machine code level (i.e. the level seen by compilers). However, pipelining at that level

6880-403: Was already used in some high-performance CISC "supercomputers" in order to reduce the instruction cycle time (despite the complications of implementing within the limited component count and wiring complexity feasible at the time). Internal microcode execution in CISC processors, on the other hand, could be more or less pipelined depending on the particular design, and therefore more or less akin to

6966-465: Was built using the latest 5-inch wafer sizes and Intel's HMOS process with a 3.5  μm feature size. This was an investment aimed at catching the competition: even upstart semiconductor companies such as Zilog and MOS Technology had introduced CPUs fabricated on depletion-mode NMOS logic before Motorola did. In fact, Motorola may have substantially lagged contemporaries in phasing out enhancement mode and metal gate, with Gunter recollecting that

7052-569: Was chosen because the 11/780 was roughly equivalent in performance to an IBM System/370 model 158–3, which was commonly accepted in the computing industry as running at 1 MIPS. Many minicomputer performance claims were based on the Fortran version of the Whetstone benchmark , giving Millions of Whetstone Instructions Per Second (MWIPS). The VAX 11/780 with FPA (1977) runs at 1.02 MWIPS. Effective MIPS speeds are highly dependent on

7138-406: Was done via ordinary (non duplicated) internal buses, or even the external bus, it would demand extra cycles every time, and thus be quite inefficient. Even in balanced high-performance designs, highly encoded and (relatively) high-level instructions could be complicated to decode and execute efficiently within a limited transistor budget. Such architectures therefore required a great deal of work on

7224-412: Was set at 1 million instructions per second (MIPS). They wanted the design to not only win back microcomputer vendors like Apple Computer and Tandy , but also minicomputer companies like NCR and AT&T . The team decided to abandon an attempt at backward compatibility with the 6800, as they felt the 8-bit designs were too limited to be the basis for new designs. The new system was influenced by

7310-750: Was the most commercially important utilisation of the 68008. Helix Systems (in Missouri, United States) designed an extension to the SWTPC SS-50 bus , the SS-64, and produced systems built around the 68008 processor. While the adoption of RISC and x86 displaced the 68000 series as desktop/workstation CPU, the processor found substantial use in embedded applications. By the early 1990s, quantities of 68000 CPUs could be purchased for less than 30  USD per part. The 68000 also saw great success as an embedded controller. As early as 1981, laser printers such as

7396-483: Was then the weighted sum of the average execution speed for instructions in each class. The speed of a given CPU depends on many factors, such as the type of instructions being executed, the execution order and the presence of branch instructions (problematic in CPU pipelines). CPU instruction rates are different from clock frequencies, usually reported in Hz , as each instruction may require several clock cycles to complete or

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