By Dave Simpson
Showing that the venerable interface still has plenty of life left, the SCSI Trade Association recently outlined the next two generations of the specification. The current generation is Ultra160 SCSI, with a theoretical maximum transfer rate of 160MBps. Ultra160 SCSI adds to previous generations three key features: double-edge (or double-transition) clocking, cyclical redundancy checking (CRC), and domain validation.
The next generation, Ultra320 SCSI, will add a number of features, including:
- Packetized protocol, for more efficient bus management
- Quick Arbitrate & Select (QAS), for faster switching between devices
- Skew and Intersymbol Interference (ISI) compensation, for higher reliability at faster speeds
- Margining, for better signal integrity
According to Mark Delsman, vice president of engineering at Adaptec and a STA board member, Ultra320 SCSI devices will begin to ship around the end of this year. Delsman says that the performance goal of each generation of the interface is to maintain a 4x speed advantage over hard disk drive media rates, which are currently at about 35MBps.
The next generation will be the 640MBps Ultra640 SCSI specification, due around 2003. For more information: visit www.scsita.org.