Motorola ceased development of the 680x0 series architecture in 1994, replacing it with the PowerPCRISC architecture, which was developed in conjunction with IBM and Apple Computer as part of the AIM alliance.
Family members
Generation one (internally 16/32-bit, and produced with 8-, 16-, and 32-bit interfaces)
The Genesis has a 68000 clocked at 7.67MHz as its main CPU.
The 680x0 line of processors has been used in a variety of systems, from high-end Texas Instruments calculators (the TI-89, TI-92, and Voyage 200 lines) to all of the members of the Palm Pilot series that run Palm OS 1.x to 4.x (OS 5.x is ARM-based), and even radiation-hardened versions in the critical control systems of the Space Shuttle.
The first several versions of Adobe's PostScript interpreters were 68000-based. The 68000 in the Apple LaserWriter and LaserWriter Plus was clocked faster than the version used then in Macintosh computers. A fast 68030 in later PostScript interpreters, including the standard resolution LaserWriter IIntx, IIf and IIg (also 300 dpi), the higher resolution LaserWriter Pro 600 series (usually 600dpi, but limited to 300dpi with minimum RAM installed) and the very high resolution Linotronic imagesetters, the 200PS (1500+dpi) and 300PS (2500+dpi). Thereafter, Adobe generally preferred a RISC for its processor, as its competitors, with their PostScript clones, had already gone with RISCs, often an AMD 29000-series. The early 68000-based Adobe PostScript interpreters and their hardware were named for Cold War-era U.S. rockets and missiles: Atlas, Redstone, etc.
Microcontrollers derived from the 68000 family have been used in a huge variety of applications. CPU32 and ColdFire microcontrollers have been manufactured in the millions as automotive engine controllers.
Many proprietary video editing systems used 68000 processors, such as the MacroSystem Casablanca, which was a black box with an easy to use graphic interface (1997). It was intended for the amateur and hobby videographer market. It is also worth noting its earlier, bigger and more professional counterpart, the "DraCo" (1995). The groundbreaking Quantel Paintbox series of early based 24-bit paint and effects system was originally released in 1981 and during its lifetime it used nearly the entire range of 68000 family processors, with the sole exception of the 68060, which was never implemented in its design. Another contender in the video arena, the Abekas 8150 DVE system, used the 680EC30, and the Play Trinity, later renamed Globecaster, uses several 68030s. The Bosch FGS-4000/4500 Video Graphics System manufactured by Robert Bosch Corporation, later BTS (1983), used a 68000 as its main processor; it drove several others to perform 3D animation in a computer that could easily apply Gouraud and Phong shading. It ran a modified Motorola VERSAdos operating system.
People who are familiar with the PDP-11 or VAX usually feel comfortable with the 68000 series. With the exception of the split of general-purpose registers into specialized data and address registers, the 68000 architecture is in many ways a 32-bit PDP-11.
It had a more orthogonal instruction set than those of many processors that came before (e.g., 8080) and after (e.g., x86). That is, it was typically possible to combine operations freely with operands, rather than being restricted to using certain addressing modes with certain instructions. This property made programming relatively easy for humans, and also made it easier to write code generators for compilers.
The 68000 series 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.
In addition, it has 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 "zero" (Z), "carry" (C), "overflow" (V), "extend" (X), and "negative" (N). The "extend" (X) flag deserves special mention, because it is separate from the carry flag. This permits the extra bit from arithmetic, logic, and shift operations to be separated from the carry for flow-of-control and linkage.
While the 68000 had a 'supervisor mode', it did not meet the Popek and Goldberg virtualization requirements due to the single instruction 'MOVE from SR', which copies the status register to another register, being unprivileged but sensitive. In the Motorola 68010 and later, this was made privileged, to better support virtualization software.
The 68000 series instruction set can be divided into the following broad categories:
There is no equivalent to the x86 CPUID instruction to determine what CPU or MMU or FPU is present.
The Motorola 68020 added some new instructions that include some minor improvements and extensions to the supervisor state, several instructions for software management of a multiprocessing system (which were removed in the 68060), some support for high-level languages which did not get used much (and was removed from future 680x0 processors), bigger multiply (32×32→64 bits) and divide (64÷32→32 bits quotient and 32 bits remainder) instructions, and bit field manipulations.
Register indirect with index register and 8-bit signed offset e.g. 8(A0,D0) or 8(A0,A1)
For (A0)+ and −(A0), the actual increment or decrement value is dependent on the operand size: a byte access adjusts the address register by 1, a word by 2, and a long by 4.
PC (program counter) relative with displacement
Relative 16-bit signed offset, e.g. 16(PC). This mode was very useful for position-independent code.
Relative with 8-bit signed offset with index, e.g. 8(PC,D2)
Absolute memory location
Either a number, e.g. "$4000", or a symbolic name translated by the assembler
Most assemblers used the "$" symbol for hexadecimal, instead of "0x" or a trailing H.
There were 16 and 32-bit versions of this addressing mode
Immediate mode
Data stored in the instruction, e.g. "#400"
Quick immediate mode
3-bit unsigned (or 8-bit signed with moveq) with value stored in opcode
In addq and subq, 0 is the equivalent to 8
e.g. moveq #0,d0 was quicker than clr.l d0 (though both made D0 equal to 0)
Plus: access to the status register, and, in later models, other special registers.
The Motorola 68020 added a scaled indexing address mode, and added another level of indirection to many of the pre-existing modes.
Most instructions have dot-letter suffixes, permitting operations to occur on 8-bit bytes (".b"), 16-bit words (".w"), and 32-bit longs (".l").
Most instructions are dyadic, that is, the operation has a source, and a destination, and the destination is changed. Notable instructions were:
Arithmetic: ADD, SUB, MULU (unsigned multiply), MULS (signed multiply), DIVU, DIVS, NEG (additive negation), and CMP (a comparison done by subtracting the arguments without storing the result, setting the status bits)
Logic: EOR (exclusive or), AND, NOT (logical not), OR (inclusive or)
Shifting: (logical, i.e. right shifts put zero in the most-significant bit) LSL, LSR, (arithmetic shifts, i.e. sign-extend the most-significant bit) ASR, ASL, (rotates through eXtend and not) ROXL, ROXR, ROL, ROR
Bit test and manipulation in memory or data register: BSET (set to 1), BCLR (clear to 0), BCHG (invert) and BTST (no change). All of these instructions first test the destination bit and set (clear) the CCR Z bit if the destination bit is 0 (1), respectively.
Multiprocessing control: TAS, test-and-set, performed an indivisible bus operation, permitting semaphores to be used to synchronize several processors sharing a single memory
Flow of control: JMP (jump), JSR (jump to subroutine), BSR (relative address jump to subroutine), RTS (return from subroutine), RTE (return from exception, i.e. an interrupt), TRAP (trigger a software exception similar to software interrupt), CHK (a conditional software exception)
Branch: Bcc (where the "cc" specified one of 14 tests of the condition codes in the status register: equal, greater than, less-than, carry, and most combinations and logical inversions, available from the status register). Of the remaining two possible conditions, always true and always false, BRA (branch always) has a separate mnemonic, and BSR (branch to subroutine) takes the encoding that would otherwise have been 'branch never'.
Decrement-and-branch: DBcc (where "cc" was as for the branch instructions), which, provided the condition was false, decremented the low word of a D-register and, if the result was not -1 ($FFFF), branched to a destination. This use of −1 instead of 0 as the terminating value allowed the easy coding of loops that had to do nothing if the count was 0 to start with, with no need for another check before entering the loop. This also facilitated nesting of DBcc.
Motorola mainly used even numbers for major revisions to the CPU core such as 68000, 68020, 68040 and 68060. The 68010 was a revised version of the 68000 with minor modifications to the core, and likewise the 68030 was a revised 68020 with some more powerful features, none of them significant enough to classify as a major upgrade to the core.
There was no 68050, though at one point it was a project within Motorola. Odd-numbered releases had always been reactions to issues raised within the prior even numbered part; hence, it was generally expected that the 68050 would have reduced the 68040's power consumption (and thus heat dissipation), improved exception handling in the FPU, used a smaller feature size and optimized the microcode in line with program use of instructions. Many of these optimizations were included with the 68060 and were part of its design goals. For any number of reasons, likely that the 68060 was in development, that the Intel 80486 was not progressing as quickly as Motorola assumed it would, and that 68060 was a demanding project, the 68050 was cancelled early in development.
There is also no revision of the 68060, as Motorola was in the process of shifting away from the 68000 and 88k processor lines into its new PowerPC business, so the 68070 was never developed. Had it been, it would have been a revised 68060, likely with a superior FPU (pipelining was widely speculated upon on Usenet).
There was a CPU with the 68070 designation, which was a licensed and somewhat slower version of the 16/32-bit 68000 with a basic DMA controller, I²C host and an on-chip serial port. This 68070 was used as the main CPU in the PhilipsCD-i. This CPU was, however, produced by Philips and not officially part of Motorola's 680x0 lineup.
Last generation
The 4th-generation 68060 provided equivalent functionality (though not instruction-set-architecture compatibility) to most of the features of the Intel P5 microarchitecture.
An Arizona-based company, Edge Computer Corp, reportedly founded by former Honeywell designers, produced processors compatible with the 68000 series, these being claimed as having "a three to five times performance – and 18 to 24 months’ time – advantage" over Motorola's own products.[21] In 1987, the company introduced the Edge 1000 range of "32-bit superminicomputers implementing the Motorola instruction set in the Edge mainframe architecture", employing two independent pipelines - an instruction fetch pipeline (IFP) and operand executive pipeline (OEP) - relying on a branch prediction unit featuring a 4096-entry branch cache, retrieving instructions and operands over multiple buses.[22] An agreement between Edge Computer and Olivetti subsequently led to the latter introducing products in its own "Linea Duo" range based on Edge Computer's machines.[23] The company was subsequently renamed to Edgcore Technology Inc.[24]:12 (also reported as Edgecore Technology Inc.[25]). Edgcore's deal with Olivetti in 1987 to supply the company's E1000 processor was followed in 1989 by another deal with Philips Telecommunications Data Systems to supply the E2000 processor, this supporting the 68030 instruction set and reportedly offering a performance rating of 16 VAX MIPS.[26] Similar deals with Nixdorf Computer and Hitachi were also signed in 1989.[27][28]
Edge Computer reportedly had an agreement with Motorola.[25] Despite increasing competition from RISC products, Edgcore sought to distinguish its products in the market by emphasising its "alliance" with Motorola, employing a marketing campaign drawing from Aesop's fables with "the fox (Edgecore) who climbs on the back of the stallion (Motorola) to pluck fruit off the higher branches of the tree".[29] Other folktale advertising themes such as Little Red Riding Hood were employed.[30] With the company's investors having declined to finance the company further, and with a number of companies having been involved in discussions with other parties, Arix Corp. announced the acquisition of Edgcore in July 1989.[28] Arix was reportedly able to renew its deal with Hitachi in 1990, whereas the future of previous deals with Olivetti and Philips remained in some doubt after the acquisition of Edgcore.[31]
In 1992, a company called International Meta Systems (IMS) announced a RISC-based CPU, the IMS 3250, that could reportedly emulate the "Intel 486 or Motorola 68040 at full native speeds and at a fraction of their cost". Clocked at 100MHz, emulations had supposedly been developed of a 25MHz 486 and 30MHz 68040, including floating-point unit support, with the product aiming for mid-1993 production at a per-unit cost of $50 to 60.[32] Amidst the apparent proliferation of emulation support in processors such as the PowerPC 615, in 1994, IMS had reportedly filed a patent on its emulation technology but had not found any licensees.[33] Repeated delays to the introduction of this product, blamed on one occasion on "a need to improve the chip's speech-processing capabilities",[34] apparently led to the company seeking to introduce another chip, the Meta6000, aiming to compete with Intel's P6 products.[35] Ultimately, IMS entered bankruptcy having sold patents to a litigator, TechSearch, who in 1998 attempted to sue Intel for infringement of an IMS patent.[36] TechSearch reportedly lost their case but sought to appeal, also seeking to sue Intel for "libel and slander" on the basis of comments made by an Intel representative who had characterised TechSearch's business model unfavourably in remarks to the press.[37]
After the mainline 68000 processors' demise, the 68000 family has been used to some extent in microcontroller and embedded microprocessor versions. These chips include the ones listed under "other" above, i.e. the CPU32 (aka 68330), the ColdFire, the QUICC and the DragonBall.
With the advent of FPGA technology an international team of hardware developers have re-created the 68000 with many enhancements as an FPGA core. Their core is known as the 68080 and is used in Vampire-branded Amiga accelerators.[38]
During the 1980s and early 1990s, when the 68000 was widely used in desktop computers, it mainly competed against Intel's x86 architecture used in IBM PC compatibles. Generation 1 68000 CPUs competed against mainly the 16-bit8086, 8088, and 80286. Generation 2 competed against the 80386 (the first 32-bit x86 processor), and generation 3 against the 80486. The fourth generation competed with the P5Pentium line, but it was not nearly as widely used as its predecessors, since much of the old 68000 marketplace was either defunct or nearly so (as was the case with Atari and NeXT), or converting to newer architectures (PowerPC for the Macintosh and Amiga, SPARC for Sun, and MIPS for Silicon Graphics (SGI)).
There are dozens of processor architectures that are successful in embedded systems. Some are microcontrollers which are much simpler, smaller, and cheaper than the 68000, while others are relatively sophisticated and can run complex software. Embedded versions of the 68000 often compete with processor architectures based on PowerPC, ARM, MIPS, SuperH, and others.
The Intel 486, officially named i486 and also known as 80486, is a microprocessor introduced in 1989. It is a higher-performance follow-up to the Intel 386. It represents the fourth generation of binary compatible CPUs following the 8086 of 1978, the Intel 80286 of 1982, and 1985's i386.
The Motorola 68000 is a 16/32-bit complex instruction set computer (CISC) microprocessor, introduced in 1979 by Motorola Semiconductor Products Sector.
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 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.
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.
The Motorola 68060 ("sixty-eight-oh-sixty") is a 32-bit microprocessor from Motorola released in April 1994. It is the successor to the Motorola 68040 and is the highest performing member of the 68000 series. Two derivatives were produced, the 68LC060 and the 68EC060.
PowerPC is a reduced instruction set computer (RISC) instruction set architecture (ISA) created by the 1991 Apple–IBM–Motorola alliance, known as AIM. PowerPC, as an evolving instruction set, has been named Power ISA since 2006, while the old name lives on as a trademark for some implementations of Power Architecture–based processors.
The Pentium is a microprocessor introduced by Intel on March 22, 1993. It is the first CPU using the Pentium brand. Considered the fifth generation in the x86 (8086) compatible line of processors, succeeding the i486, its implementation and microarchitecture was internally called P5.
The NS32000, sometimes known as the 32k, is a series of microprocessors produced by National Semiconductor. Design work began around 1980 and it was announced at the International Solid-State Circuits Conference in April 1981. The first member of the family came to market in 1982, briefly known as the 16032 before becoming the 32016. It was the first general-purpose microprocessor on the market that used 32-bit data internally: the Motorola 68000 had 32-bit registers and instructions to perform 32-bit arithmetic, but used a 16-bit ALU for arithmetic operations on data, and thus took twice as long as the 32016 to perform those arithmetic operations. However, the 32016 contained many bugs and often could not be run at its rated speed. These problems, and the presence of the otherwise similar 68000 which had been available since 1980, led to little use in the market despite considerable early interest.
The Motorola MC68010 and Motorola MC68012 are 16/32-bit microprocessors from Motorola, released in 1982 as successors to the Motorola 68000. The 68010 and 68012 added virtualization features, optimized loops and fixed several small flaws to the 68000. The MC68010 variants were pin compatible with its predecessor while the MC68012 is an 84-pin PGA version with its directly accessible memory space extended to 2 GiB.
The 88000 is a RISC instruction set architecture developed by Motorola during the 1980s. The MC88100 arrived on the market in 1988, some two years after the competing SPARC and MIPS. Due to the late start and extensive delays releasing the second-generation MC88110, the m88k achieved very limited success outside of the MVME platform and embedded controller environments. When Motorola joined the AIM alliance in 1991 to develop the PowerPC, further development of the 88000 ended.
The Amiga 2000 (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 and one 5.25" bay that could be used by a 5.25" floppy drive, a hard drive, or CD-ROM once they became available.
In computer architecture, 32-bit computing refers to computer systems with a processor, memory, and other major system components that operate on data in 32-bit units. Compared to smaller bit widths, 32-bit computers can perform large calculations more efficiently and process more data per clock cycle. Typical 32-bit personal computers also have a 32-bit address bus, permitting up to 4 GB of RAM to be accessed, far more than previous generations of system architecture allowed.
Originally, the word computing was synonymous with counting and calculating, and the science and technology of mathematical calculations. Today, "computing" means using computers and other computing machines. It includes their operation and usage, the electrical processes carried out within the computing hardware itself, and the theoretical concepts governing them.
The Atari Falcon030, released in 1992, is the final personal computer from Atari Corporation. A high-end model of the Atari ST line, the machine is based on a Motorola 68030 CPU and a Motorola 56001 digital signal processor, which distinguishes it from most other microcomputers of the era. It includes a new VIDEL programmable graphics system which greatly improves graphics capabilities.
The Motorola 68881 and Motorola 68882 are floating-point units (FPUs) used in some computer systems in conjunction with Motorola's 32-bit 68020 or 68030 microprocessors. These coprocessors are external chips, designed before floating point math became standard on CPUs. The Motorola 68881 was introduced in 1984. The 68882 is a higher performance version produced later.
In computer architecture, 16-bit integers, memory addresses, or other data units are those that are 16 bits wide. Also, 16-bit central processing unit (CPU) and arithmetic logic unit (ALU) architectures are those that are based on registers, address buses, or data buses of that size. 16-bit microcomputers are microcomputers that use 16-bit microprocessors.
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