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SBus, PCI, USB etc... a user's introduction to the busses used in SPARC based computers what they do, market trends and 3rd party support.

SPARC history
SPARC History
Spellabyte and Terrorbyte loved sitting around
the campfire, discussing the good old days of
SPARC computing.

650MHz SPARC VME SBCs from Themis Computer
from Themis Computer

by Zsolt Kerekes, Publisher - SPARC Product Directory

If you're taking your first look at SPARC based systems we hope this simple non technical guide (first published in 1997) will help you a feel for the basic expansion busses you'll find in SPARC based systems.

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Historically the main expansion busses used for adding in cards and modules in SPARC based systems were (in order of introduction)

Expansion Bus

First appearance in a SPARC system

First production model in which used



Sun Microsystems Sun-4 deskside server.



Sun Microsystems Sun-4 deskside server.



Sun Microsystems SPARCstation 1 desktop workstation.



Sun Microsystems SPARCserver 600MP deskside and datacenter server.



Sun Microsystems Voyager transportable.



Sun Microelectronics - SPARCengine Ultra AX oem motherboard.

Compact PCI





Sun Microsystems - Sun Blade 100 workstation



Themis Computer, slot expansion for rugged enterprise servers
Serial Attached SCSI 2005 Sun Microsystems - Sun Fire X4100

More information about each of these subjects is given below.

VMEbus in SPARC systems

VME was the most commonly used I/O expansion bus interface in the early years of the SPARC systems market, (1987 to 1992). Its function was replaced in most SPARC systems by the widespread adoption of SBus. However new models of SPARC systems at the leading edge of technology continue to be used in embedded systems. The main manufacturers of SPARC based VME cards are FORCE COMPUTERS, THEMIS COMPUTER and General Micro Systems. Server manufacturer Auspex Systems has also continued to use VMEbus within its NFS servers.

The VME-bus is an asynchronous non-multiplexed bus which has 32/64 bit wide data and address busses. Although the VME-bus specification, IEEE-1014, is now over 12 years old its performance is continously being enhanced. In January 1997, Bustronic and Arizona Digital announced an enhanced backplane technology which extends the VMEbus transfer rate to 320M bytes/second.

Hundreds of manufacturers make VMEbus cards and systems. Despite the age of this standard it is likely that VME products will continue to be available well beyond the year 2,000. There are over 4,000 different types of VME compatible boards. Readers who require more more information are recommended to refer to the online VMEbus Product Directory. This is the most comprehensive reference listing of VME-bus boards and suppliers. It is produced by the VME International Trade Association (VITA). More information and a link to the VME directory is available via our web file other information sources.

SBus in SPARC systems.

SBus is currently (Q3 1997) the most important expansion bus available in SPARC systems. It's used in most of the installed base, and appears in over 70% of current models.

SBus was originally developed by Sun Microsystems. To encourage its widespread adoption Sun used a "feeless" licensing strategy and put the specification in the public domain. It was later adopted as IEEE standard P1496.

SBus is a mezzanine bus designed to give low cost I/O expansion in workstations. It is not used outside the SPARC systems market. Originally specified as a 32 bit bus, the performance has been extended by D64 operation and clock doubling to a throughput capability of 200M bytes/second.

In the history of SBus over 250 manufacturers have introduced production models of cards and systems using SBus. Since 1992, these products and suppliers have been listed in the SBus Product Directory, which was renamed in 1996 the SPARC Product Directory. To get an idea of the range of products available click on SBus cards in the SPARC Product Directory

Outlook for SBus. The applications legacy of over 1,000 types of SBus product from over 250 manufacturers in 3,000,000+ systems means that SBus will continue as a prime contender in most SPARC user sites during the next few years. However, its role in new high performance SPARC systems is getting displaced by PCI.

MBus in SPARC systems

The MBus is a multiprocessor bus introduced by Sun Microsystems in its 600MP server range (in Q4 1991). It became extremely popular in the high volume 32 bit CPU based SPARCstation models 10, 20, and compatibles.

Sun discontinued its MBus workstations in Q4 1996, however, MBus continued to be supported by most other manufacturers of SPARC based computers for a year or so after that. It is now obsolete.

Only two chip manufacturers have made MBus compatible processors. They are Sun Microelectronics (SuperSPARC), and the now defunct Ross Technology (HyperSPARC.)

MBus supports multiprocessing and has a bus bandwidth of 320M byte/second. Part of the specification includes a mechanical/electrical compatible socket interface for installing newer faster CPU modules. The technique of upgrading a computer by designing a compatible processor module footprint was first demonstrated successfully in the PC market where module level upgrades to new generations of processor were used by major vendors for several years. At the chip level Intel Corporation has used this technique of user upgradeability in its 486SX and 486DX2, and 486DX4 Overdrive family of processors.

In the SPARC world the performance range of compatible processors enables owners of 40MHz systems to upgrade to processors with 150MHz to 200MHz clock speeds. Users can also install upto 4 processors in most original MBus systems. This easy upgradability has benefited oem's as well as users, because it reduces the number of design changes needed on processor motherboards.

PCMCIA in SPARC systems

PCMCIA is a bus standard designed for portable computers in the Intel PC market. The first production SPARC system using it was Sun's SPARCstation Voyager transportable introduced in 1994. This was not a very successful machine from the market point of view because the processor was underpowered compared to competing desktop models, and it was more like a transportable than a true portable. Sun exited the portable workstation market when it discontinued this model.

SPARC portable manufacturers include :- Tadpole Technology, RDI Computer and Telos Systems Integration. Tadpole invented the first SPARC portable in 1992. All current SPARC portable models include PCMCIA as an expansion option.

PCI in SPARC systems

The first production SPARC system with a Solaris supported PCI interface was the SPARCengine Ultra AX oem motherboard launched by Sun Microelectronics in Q4 1996. Sun Microelectronics had previously announced PCI support for both its low cost 32 bit microSPARC chip, and the high performance 64 bit UltraSPARC family.

Using the SPARCengine Ultra AX, the only thing needed for a computer manufacturer to ship a SPARC workstation is an enclosure, power supply and peripherals. A number of manufacturers launched PCI based SPARC systems using this technology during the first quarter of 1997, for example EIS Computers (now renamed StarBox Netsystems) and it opened the door for a new generation of very low cost SPARC systems using "PC priced" graphics and communications cards. Sun Microsystems launched its own workstation using native PCI expansion technology, the Ultra 30, in Q3 97.

PCI is one of the world's most successful computer busses and was originally designed for use in Intel based PC s. It has since been incoporated in most competing RISC based computers including IBM's PowerPC and DEC's Alpha. SPARC supported PCI products can be found on the SBus and PCI cards list.

...Later:- jan 2006 - Digi International has published a good overview article about PCI (pdf).

Compact PCI in SPARC systems

Compact PCI is a new bus/backplane standard for industrial and embedded telecoms applications. The first SPARC processor system using this standard was introduced in Q3 1997 by FORCE COMPUTERS. THEMIS COMPUTER launched a SPARC Compact PCI card in Q1 1998.

This standard combines the mechanical form factor of Eurocards (as previously used in VMEbus systems) with the electrical and timing characteristics of the PCI-bus. The PCI Industrial Manufacturers Group web site includes over 400 manufacturers which make compatible cards.

See also:- compact PCI SPARC processor cards, compact PCI Ethernet NICs, CompactPCI Systems magazine

USB in SPARC systems

The USB (for Universal Serial Bus) is a low cost serial bus which can provide upto 12 Mb/S. That's about 100 times faster than the RS-232 style serial interfaces used in earlier generations of computers.

First developed in 1996, the USB is now widely used in Macs, PC's and even Linux systems. USB is typically used to connect devices such as printers, scanners, keyboards, digital cameras, MP3 players and low speed storage devices.

The first SPARC processor system using this standard was introduced in February 2001 by Sun Microsystems when it launched the Sun Blade[tm] 100 workstation, the first ever 64-bit workstation priced under $1,000.

See also:- USB - drives, USB trade organization

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