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IEEE accepts SBus as an industry standard
Conceived as one company's solution to customer demands for greater I/O
flexibility and bandwidth in a RISC and Unix environment, SBus has
recently been accepted as a standard by the IEEE. The standard is called
1496-1993 “Standard for a Chip and Module Interconnect: SBus.” Acceptance
by the IEEE is a result of a year-long push by SBus advocates, backed by a
steady flow of I/O products made available since SBus's introduction in
1989. The IEEE specification provides the full electrical, logical, and
mechanical information necessary for an SBus interface. The SBus
interface solves the flexibility and bandwidth problem by offering a
bandwidth of up to 160 Mbytes/s on a postcard-size board that mounts in a
host-based mezzanine slot. The standard allows for 32-bit virtual
addressing, 32- and 64-bit data paths, and direct virtual-memory access.
The boards can handle up to 128-Mbyte burst transfers and have master,
slave, and interrupt capability. In addition, off-the-shelf availability
makes SBus an attractive alternative to home-grown solutions in
applications where time to market is critical.
According to technology market researcher Venture Development Corp.
(Natick, MA), the SBus market has seen consistent growth in the last
couple of years, particularly in the areas of communications, graphics,
and video. The company quotes market value figures of $22.2 million in
1990, increasing to some $84.7 million in 1992. This growth is expected to
continue, reaching $120 million by the end of this year.
Originally developed by Sun Microsystems Computer Corp. (Mountain View,
CA) for its Sparcstation 1 Unix workstation, SBus has also found a home in
VMEbus applications. For example, although Greenspring Computers (Menlo
Park, CA) has already nurtured its IndustryPack mezzanine standard to
fruition on the VMEbus, there is still ample room for SBus. “SBus is a
very high-end I/O interface standard, and as such will complement, not
compete with, its IndustryPack counterparts,” said Wayne Fischer, director
of strategic programs at Force Computers (San Jose, CA). Fischer heads the
IEEE P1496 Working Group. He lists computer tomography, portable
ultrasound, flight simulation, and an asynchronous transfer mode interface
as currently available high-end SBus implementations.
–Patrick Mannion
CAPTION:
While Sun Microsystems' openness with respect to the SBus specification
contributed greatly to the standard's popularity, it also helped jumpstart
the IEEE SBus ratification process.
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