This paper attempts to describe in general terms, the architecture, usage, and attributes of the various interfaces found on data storage devices. These storage devices include Hard Disk Drives (HDD), Optical Disk Drives, (ODD), and Solid State Drives (SSD). Also included are Small Form Factor (SFF) storage devices such as 1.8”, 1”, and 0.85” mechanical and solid state devices.

   There are two main categories of interfaces: parallel and serial. Both have certain advantages over the other but as of this writing, high speed serial interfaces are gaining market share.

   A serial interface can be defined as the process of sending data one bit at a time sequentially over a cable or circuit traces (the transmission line). This is in contrast to a parallel interface where all bits of a symbol (bytes or words) are sent together with a clock and control signals.

   Serial communication simplifies the cable and connector components and can typically be used over longer transmission lines but requires a much higher frequency of operation in order to accomplish the equivalent bandwidth of a parallel interface. Parallel interfaces have synchronization problems which limit the data rate. Also the cost and complexity of the cable and connectors are more significant for parallel schemes.

   Flexstar supports these various interfaces with either custom built or off-the-shelf Host Bus Adapters (HBA’s). Some interfaces can be accommodated via native support from within our Single Board Computer (SBC).