MBus is a

computer bus In computer architecture, a bus (shortened form of the Latin '' omnibus'', and historically also called data highway or databus) is a communication system that transfers data between components inside a computer, or between computers. This ex ...

designed and implemented by

Sun Microsystems Sun Microsystems, Inc. (Sun for short) was an American technology company that sold computers, computer components, software, and information technology services and created the Java programming language, the Solaris operating system, ZFS, the ...

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 electronic circuitry that executes instructions comprising a computer program. The CPU performs basic arithmetic, logic, controlling, an ...

motherboard A motherboard (also called mainboard, main circuit board, mb, mboard, backplane board, base board, system board, logic board (only in Apple computers) or mobo) is the main printed circuit board (PCB) in general-purpose computers and other expand ...

and

main memory Computer 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 processing unit (CPU) of a computer ...

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 S ...

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

multiprocessor Multiprocessing 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. There ar ...

SPARC SPARC (Scalable Processor Architecture) is a reduced instruction set computer (RISC) instruction set architecture originally developed by Sun Microsystems. Its design was strongly influenced by the experimental Berkeley RISC system developed ...

-based system, the

SPARCserver The SPARCstation, SPARCserver and SPARCcenter product lines are a series of SPARC SPARC (Scalable Processor Architecture) is a reduced instruction set computer (RISC) instruction set architecture originally developed by Sun Microsystems. ...

600MP series (launched in 1991), and later found use in the SPARCstation 10 and

SPARCstation 20 The SPARCstation 20 or SS20 (code-named ''Kodiak'') is a discontinued Sun Microsystems workstation introduced in March 1994 based on the SuperSPARC or hyperSPARC CPU. It is one of the last models in the SPARCstation family of Sun " pizza box" com ...

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

multiprocessing Multiprocessing 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. There ar ...

configuration with up to eight CPUs 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 Integer (computer science), integers, memory addresses, or other Data (computing), data units are those that are 64 bits wide. Also, 64-bit central processing unit, CPUs and arithmetic logic unit, ALUs are those ...

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

, 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 st ...

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 6400 ...

. 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 servers ...

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, Inc.,

Hyundai Hyundai is a 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 Mobis, Korean car parts company ** Hyundai ...

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

Fujitsu is a Japanese multinational information and communications technology equipment and services corporation, established in 1935 and headquartered in Tokyo. Fujitsu is the world's sixth-largest IT services provider by annual revenue, and the la ...

, Tatung, GCS, Auspex,

ITRI The Industrial Technology Research Institute (ITRI; ) is a technology research and development institution in Taiwan. Founded in 1973, ITRI has contributed to moving Taiwan's industries from labor-intensive to innovation-driven. ITRI is hea ...

, 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 Amdahl may refer to: People * Einar Amdahl (1888-1974), Norwegian theologist * Bjarne Amdahl (1903-1968), Norwegian pianist and composer * Douglas K. Amdahl (1919–2010), American lawyer and judge from Minnesota * Gene Amdahl (1922–2015), for ...

Themis In Greek mythology and Ancient Greek religion, religion, Themis (; grc, Θέμις, Themis, justice, law, custom) is one of the twelve Titans, Titan children of Gaia and Uranus (mythology), Uranus, and the second wife of Zeus. She is the godde ...

, DTK and Kamstrup.

References

External links

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

MBus Specification
{{Computer bus Computer buses Sun Microsystems hardware