MBus (SPARC)

MBus module, Sun SuperSPARC II SM71

Two MBus connectors (top of photograph), one occupied by CPU module

MBus is a computer bus designed and implemented by Sun Microsystems for communication between high speed computer system components, such as the central processing unit, motherboard and main memory. Contrast this with SBus, used in the same machines to connect add-on cards to the motherboard.

MBus was first used in Sun's first multiprocessor SPARC-based system, the SPARCserver 600MP series (launched in 1991), and later found use in the SPARCstation 10 and SPARCstation 20 workstations. The bus permitted the integration of several microprocessors on a single motherboard, in a multiprocessing configuration with up to eight CPUs packaged in detachable MBus modules. However, in practice, the number of processors per MBus was limited to four. Single processor systems were also sold that used the MBus protocol internally, but with the CPUs permanently attached to the motherboard to lower manufacturing costs.

MBus specified a 64-bit datapath, which used 36-bit physical addressing, giving an address space 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. This corresponded 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 Series 6 and Series 7 computer systems.

History

The MBus standard was cooperatively developed by Sun and Ross Technology and released in 1991.^[1]

Manufacturers who produced computer systems using the MBus included Sun, Ross Technology, Inc., Hyundai/Axil, Fujitsu, Solbourne Computer, Tatung, GCS, Auspex, ITRI, ICL, Cray, Amdahl, Themis, DTK and Kamstrup.

References

↑ "HyperSPARC goes Hollywood; Pixar uses HyperSPARC microprocessors from Ross Technology to create final rendering of 'Toy Story'".

External links

MBus male connector

Technical and de facto standards for wired computer buses

General	System bus Front-side bus Back-side bus Daisy chain Control bus Address bus Bus contention Network on a chip Plug and play List of bus bandwidths

Standards	SS-50 bus S-100 bus Unibus VAXBI MBus STD Bus SMBus Q-Bus Europe Card Bus ISA STEbus Zorro II Zorro III CAMAC FASTBUS LPC HP Precision Bus EISA VME VXI VXS NuBus TURBOchannel MCA SBus VLB PCI PXI HP GSC bus InfiniBand UPA PCI Extended (PCI-X) AGP PCI Express (PCIe) Direct Media Interface (DMI) RapidIO Intel QuickPath Interconnect HyperTransport

Storage	ST-506 ESDI SMD Parallel ATA (PATA) SSA DSSI HIPPI Serial ATA (SATA) eSATA eSATAp mSATA SCSI Parallel SCSI SAS Fibre Channel SATA Express M.2

Peripheral	Apple Desktop Bus HIL MIDI Multibus RS-232 RS-422 RS-423 RS-485 DMX512-A IEEE-488 (GPIB) IEEE-1284 (parallel port) UNI/O ACCESS.bus 1-Wire D²B I²C SPI Parallel SCSI Profibus USB IEEE 1394 (FireWire) Camera Link External PCIe Thunderbolt

Audio	ADAT Lightpipe AES3 Intel HD Audio I²S MADI McASP S/PDIF TOSLINK

Portable	PC Card ExpressCard

Embedded	Multidrop bus CoreConnect AMBA Wishbone

Interfaces are listed by their speed in the (roughly) ascending order, so the interface at the end of each section should be the fastest. Category

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