MBus is a

computer bus In computer architecture, a bus (historically also called a data highway or databus) is a communication system that transfers data between components inside a computer or between computers. It encompasses both hardware (e.g., wires, optical ...

designed and implemented by

Sun Microsystems Sun Microsystems, Inc., often known as Sun for short, was an American technology company that existed from 1982 to 2010 which developed and sold computers, computer components, software, and information technology services. Sun contributed sig ...

for communication between high speed computer system components, such as the

central processing unit A central processing unit (CPU), also called a central processor, main processor, or just processor, is the primary Processor (computing), processor in a given computer. Its electronic circuitry executes Instruction (computing), instructions ...

motherboard A motherboard, also called a mainboard, a system board, a logic board, and informally a mobo (see #Nomenclature, "Nomenclature" section), is the main printed circuit board (PCB) in general-purpose computers and other expandable systems. It ho ...

and

main memory Computer data storage or digital data storage is a technology consisting of computer components and recording media that are used to retain digital data. It is a core function and fundamental component of computers. The central processin ...

SBus SBus is a computer bus system that was used in most SPARC-based computers (including all SPARCstations) from Sun Microsystems and others during the 1990s. It was introduced by Sun in 1989 to be a high-speed bus counterpart to their high-speed ...

is used in the same machines to connect add-on cards to the motherboard. MBus was first used in Sun's first

multiprocessor Multiprocessing (MP) is the use of two or more central processing units (CPUs) within a single computer system. The term also refers to the ability of a system to support more than one processor or the ability to allocate tasks between them. The ...

SPARC-based system, the SPARCserver 600MP series (launched in 1991), and later found use in the

SPARCstation 10 The SPARCstation 10 (codenamed ''Campus-2'') is a workstation computer made by Sun Microsystems. Announced on May 19, 1992, the SPARCstation sold for between 18,495 at the low end to US$57,995 at the high end (equivalent to $– in ). Housed in ...

and

SPARCstation 20 The SPARCstation 20 (code-named ''Kodiak'') is a workstation made by Sun Microsystems. The SPARCstation 20 was released on March 29, 1994, alongside the lower-end SPARCstation 5. The SPARCstation 20 shipped with dual SuperSPARC or hyperSPARC CPUs, ...

workstations. The bus permits the integration of several microprocessors on a single motherboard, in a

multiprocessing Multiprocessing (MP) is the use of two or more central processing units (CPUs) within a single computer system. The term also refers to the ability of a system to support more than one processor or the ability to allocate tasks between them. The ...

configuration with up to eight

CPU A central processing unit (CPU), also called a central processor, main processor, or just processor, is the primary processor in a given computer. Its electronic circuitry executes instructions of a computer program, such as arithmetic, log ...

s packaged in detachable MBus modules. In practice, the number of processors per MBus is limited to four. Single processor systems were also sold that use the MBus protocol internally, but with the CPUs permanently attached to the motherboard to lower manufacturing costs. MBus specifies a

64-bit In computer architecture, 64-bit integers, memory addresses, or other data units are those that are 64 bits wide. Also, 64-bit central processing units (CPU) and arithmetic logic units (ALU) are those that are based on processor registers, a ...

datapath A data path is a collection of functional units such as arithmetic logic units (ALUs) or multipliers that perform data processing operations, registers, and buses. Along with the control unit it composes the central processing unit (CPU). A la ...

, which uses

36-bit 36-bit computers were popular in the early mainframe computer era from the 1950s through the early 1970s. Starting in the 1960s, but especially the 1970s, the introduction of 7-bit ASCII and 8-bit EBCDIC led to the move to machines using 8-bit ...

physical address In computing, a physical address (also real address, or binary address), is a memory address that is represented in the form of a binary number on the address bus circuitry in order to enable the data bus to access a ''particular'' storage cell o ...

ing, giving an

address space In computing, an address space defines a range of discrete addresses, each of which may correspond to a network host, peripheral device, disk sector, a memory cell or other logical or physical entity. For software programs to save and retrieve ...

of 64 GB. The transfer rate is 80 MB/s sustained (320 MB/s peak) at 40 MHz, or 100 MB/s (400 MB/s peak) at 50 MHz. Bus controlling is done by an arbiter. Interrupt, reset, and timeout logic are also specified.

Related buses

Several related buses were also developed:

XBus

XBus is a packet-switched bus used in the SPARCserver 1000, SPARCcenter 2000 and

Cray CS6400 The Cray Superserver 6400, or CS6400, is a discontinued multiprocessor server computer system produced by Cray Research Superservers, Inc., a subsidiary of Cray Research, and launched in 1993. The CS6400 was also sold as the Amdahl SPARCsummit 64 ...

. This corresponds to the circuit-switched MBus, with identical electrical characteristics and physical form factor but an incompatible signalling protocol.

KBus

KBus is a high-speed interconnection system for linking multiple MBuses, used in

Solbourne Computer Solbourne Computer, Inc. was originally a vendor of computer systems based in Longmont, Colorado, United States, at first 52% owned by Matsushita. In the late 1980s and early 1990s, the company produced a range of computer workstations and server ...

Series 6 and Series 7 computer systems.

History

The MBus standard was cooperatively developed by Sun and

Ross Technology Ross Technology, Inc. was a semiconductor design and manufacturing company, specializing in SPARC microprocessors. It was founded in Austin, Texas in August 1988 by Dr. Roger D. Ross, a leading computer scientist who headed Motorola's Advanced ...

and released in 1991."HyperSPARC goes Hollywood; Pixar uses HyperSPARC microprocessors from Ross Technology to create final rendering of 'Toy Story'"
. Manufacturers who produced computer systems using the MBus included Sun, Ross Technology,

Hyundai Hyundai is a former South Korean industrial conglomerate ("''chaebol''"), which was restructured into the following groups: * Hyundai Group, parts of the former conglomerate which have not been divested ** Hyundai Asan, a real estate construction ...

Axil A leaf (: leaves) is a principal appendage of the stem of a vascular plant, usually borne laterally above ground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leaves, stem, fl ...

, Fujitsu,

, Tatung, GCS, Auspex,

ITRI Itri is a small city and ''comune'' the province of Latina, Lazio, central Italy. Itri is an agricultural centre divided in two parts by a small river, the Pontone. It lies in a valley between the Monti Aurunci and the sea, not far from the Gul ...

, ICL,

Cray Cray Inc., a subsidiary of Hewlett Packard Enterprise, is an American supercomputer manufacturer headquartered in Seattle, Washington. It also manufactures systems for data storage and analytics. Several Cray supercomputer systems are listed ...

, Amdahl,

Themis In Greek mythology and religion, Themis (; ) is the goddess and personification of justice, divine order, law, and custom. She is one of the twelve Titan children of Gaia and Uranus, and the second wife of Zeus. She is associated with oracles a ...

, DTK and Kamstrup.

References

External links

''The Rough Guide to MBus Modules'', sunhelp.org

MBus Specification
{{Sun Microsystems Computer buses Sun Microsystems hardware Computer-related introductions in 1991