SBus 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 e ...

system that was used in most

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 develope ...

-based computers (including all

SPARCstation The SPARCstation, SPARCserver and SPARCcenter product lines are a series of SPARC-based computer workstations and servers in desktop, desk side (pedestal) and rack-based form factor configurations, that were developed and sold by Sun Microsyst ...

s) from

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, t ...

and others during the 1990s. It was introduced by Sun in 1989 to be a high-speed bus counterpart to their high-speed SPARC processors, replacing the earlier (and by this time, outdated)

VMEbus VMEbus (Versa Module Europa or Versa Module Eurocard bus) is a computer bus standard, originally developed for the Motorola 68000 line of CPUs, but later widely used for many applications and standardized by the IEC as ANSI/IEEE 1014-1987. ...

used in their

Motorola Motorola, Inc. () was an American multinational telecommunications company based in Schaumburg, Illinois, United States. After having lost $4.3 billion from 2007 to 2009, the company split into two independent public companies, Motorola ...

68020 The Motorola 68020 ("''sixty-eight-oh-twenty''", "''sixty-eight-oh-two-oh''" or "''six-eight-oh-two-oh''") is a 32-bit microprocessor from Motorola, released in 1984. A lower-cost version was also made available, known as the 68EC020. In keepi ...

- and

68030 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 gener ...

-based systems and early SPARC boxes. When Sun moved to open the SPARC definition in the early 1990s, SBus was likewise standardized and became IEEE-1496. In 1997 Sun started to migrate away from SBus to the

Peripheral Component Interconnect Peripheral Component Interconnect (PCI) is a local computer bus for attaching hardware devices in a computer and is part of the PCI Local Bus standard. The PCI bus supports the functions found on a processor bus but in a standardized format ...

(PCI) bus, and today SBus is no longer used. The industry's first third-party SBus cards were announced in 1989 by Antares Microsystems; these were a

10BASE2 10BASE2 (also known as cheapernet, thin Ethernet, thinnet, and thinwire) is a variant of Ethernet that uses thin coaxial cable terminated with BNC connectors to build a local area network. During the mid to late 1980s this was the domin ...

Ethernet controller, a SCSI-SNS host adapter, a parallel port, and an 8-channel serial controller. The specification was published by Edward H. Frank and James D. Lyle. A technical guide to the bus was published in 1992 in book form by Lyle, who founded Troubador Technologies. Sun also published a set of books as a "developer's kit" to encourage third-party products. At the peak of the market over 250 manufacturers were listed in the SBus Product Directory, which was renamed to the SPARC Product Directory in 1996. SBus is in many ways a "clean" design. It was targeted only to be used with SPARC processors, so most cross-platform issues were not a consideration. SBus is based on a

big-endian In computing, endianness, also known as byte sex, is the order or sequence of bytes of a word of digital data in computer memory. Endianness is primarily expressed as big-endian (BE) or little-endian (LE). A big-endian system stores the most si ...

32-bit 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 calculati ...

address and data bus, can run at speeds ranging from 16.67 MHz to 25 MHz, and is capable of transferring up to 100 MB/s. Devices are each mapped onto a 28-bit address space (256 MB). Only eight masters are supported, although there can be an unlimited number of slaves. When the

64-bit In computer architecture, 64-bit integers, memory addresses, or other data units are those that are 64 bits wide. Also, 64-bit CPUs and ALUs are those that are based on processor registers, address buses, or data buses of that size. A ...

UltraSPARC The UltraSPARC is a microprocessor developed by Sun Microsystems and fabricated by Texas Instruments, introduced in mid-1995. It is the first microprocessor from Sun to implement the 64-bit SPARC V9 instruction set architecture (ISA). Marc Tre ...

was introduced, SBus was modified to support extended transfers of a 64 bits doubleword per cycle to produce a 200 MB/s 64-bit bus. This variant of the SBus architecture used the same form factor and was backward-compatible with existing devices, as extended transfers are an optional feature. SBus cards had a very compact form factor for the time. A single-width card was wide by long and is designed to be mounted parallel to the motherboard. This allowed for three expansion slots in the slim "

pizza box The pizza box or pizza package is a folding packaging box made of cardboard in which hot pizzas are stored for take-out. The "pizza box" also makes home delivery and takeaway substantially easier. The pizza box has to be highly resistant, c ...

" enclosure of the

SPARCstation 1 The SPARCstation 1 (Sun 4/60, code-named ''Campus'') is the first of the SPARCstation series of SPARC-based computer workstations sold by Sun Microsystems. The design originated in 1987 by a Sun spin-off company, Unisun, which was soon re-acquire ...

. The design also allows for double- or triple-width cards that take up two or three slots, as well as double-height (two 3x5 inch boards mounted in a "sandwich" configuration) cards. SBus was originally announced as both a

system bus A system bus is a single computer bus that connects the major components of a computer system, combining the functions of a data bus to carry information, an address bus to determine where it should be sent or read from, and a control bus to det ...

and a peripheral interconnect that allowed input and output devices relatively low latency access to memory. However, soon memory and

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, a ...

(CPU) speeds outpaced I/O performance. Within a year some Sun systems used MBus, another interconnection standard, as a CPU—memory bus. The SBus served as an input/output bus for the rest of its lifetime.

References

External links

SBus Specification at Bitsavers

15205-2000 - ISO/IEC 15205:2000 (IEEE Std 1496-1993) SBus -- Chip and Module Interconnect Bus
{{Authority control Computer buses Sun Microsystems hardware Motherboard expansion slot

See also

References

External links