TABLE OF CONTENTS Although the initial Serial ATA transfer rate of 150 megabytes per second is higher than the available transfer rates for parallel ATA, the overhead incurred by serializing and packetizing the traffic between host and device could adversely affect overall performance. This chapter presents an analysis of the Serial ATA protocol efficiency and compares it with the parallel ATA protocol efficiency. [1] Since one of the benefits of Serial ATA is data reliability accommodated by the strong CRC coverage for all exchanged packets, this chapter includes an analysis of the protocol reliability accommodated by the interface raw error rate and the data integrity features built into the protocol.
The performance and efficiency of a Serial ATA solution is clearly implementation dependent. Some designs might be more sophisticated or efficient than others, and this difference is reflected in the overall performance that a design can realize. Some aspects of performance, however, are inherent in the protocol and cannot be overcome regardless of the ingenuity of the designer. For purposes of this comparison of Serial ATA protocol efficiency, we have considered only those performance factors that are inherent to the protocol. We have factored out implementation-specific aspects of the protocol.
For example, one inherent factor in the protocol is the amount of time it takes to transfer a command from the host to the device. In Serial ATA, this transfer is accomplished by transmitting a Register FIS that is 20 bytes long. At 150 megabytes per second the inherent amount...
