IBM Corp is making engineering details of its Serial Storage Architecture available to other manufacturers, in an attempt to establish the disk interface standard as the standard for transferring data between computers and peripherals. The move comes just weeks after Quantum Corp, Seagate Techology Inc and Hewlett-Packard Co, backers of the rival Fibre Channel technology, undertook an international ‘hearts and minds’ campaign to win manufacturers over to their technology (CI No 2,599). Ironically IBM, in partnership with Hewlett-Packard, with cheerleading from Sun Microsystems Inc, has also been active in developing Fibre Channel Arbitrated Loop, but it appears to be pushing Serial Storage Architecture over the other. Both camps, however, agree that SCSI will not meet the requirements of the increased performance capabilities of personal computers and peripherals. Bottlenecks can occur as concurrent input-output requests from a variety of peripherals contend for access to the processor. IBM says that with a serial interface, the level of contention is greatly reduced, providing a substantial increase in data throughput. IBM will provide details about Serial Storage Architecture that will facilitate the design of chips for the technology, with a free right to use this information subject to patent rights. In addition, IBM will license some patents that cover the Serial Storage Architecture interface amd are needed to implement it. IBM will charge a one-time fee of $5,000, or it will cross-license. IBM says that more than 25 companies have already received the free information package.
Gallium Arsenide
It is also publicising the fact that some 20 companies have joined the SSA Industry Association, saying this indicates strong support for Serial Storage Architecture in the marketplace. IBM’s technology is said to simplify cabling requirements, thus reducing cost. It has something called spatial re-use that enables data to be transferred concurrently at high speeds between many pairs of serially connected peripherals, without the need to route the data through the processor. Serial Storage Architecture’s fundamental building block is a single port capable of carrying on two 20Mbps conversations at once: one inbound and one outbound. A Serial Storage Architecture connection is two dual-port nodes, each capable of carrying on four simultaneous con versations, for a total interface bandwidth of 80Mbps. Fibre Channel is also able to transmit large data files bi-directionally but a speeds of 1Gbps from computer to computer, or computer to peripheral, or to storage device. IBM says that Serial Storage Architecture’s dual-port, full-duplex architecture enables peripherals to be connected in loop configurations that are designed to contain no single point of failure. VLSI Technology Inc, San Jose, California has already announced the first silicon building-block implementation of this dual-ported interface function (CI No 2,573). VLSI is backing Serial Storage Architecture because it believes the standard simplifies cabling, offers fault-tolerance and hot plugging as well as performance advantages in computer storage applications. IBM says that the techology’s low cost is achieved through the use of compact cables and connectors and by embedding all circuitry into a single CMOS chip. Until recently, most Fibre Channel interfaces were based on Gallium Arsenide, but have recently demonstrated CMOS-based products. IBM says its technology’s key advantages with respect to Fibre Channel Arbitrated Loop are its suitability of use in devices intended for attachment to a range of machines, from mainframes to personal computers, but Fibre Channel is claimed to do this as well; it is cheaper, although the introduction of CMOS into Fibre Channel might reduce this advantage; it’s more reliable; and provides an easier migration path for systems currently operating with SCSI. Fibre Channel is claimed to be faster than Serial Storage Architecture; said to go further, up to six miles with fibre optics; has hot-plug capacity; an
d offers bandwidth support for high data rates.
