Introduction
The parallel Advanced Technology Attachment (ATA) architecture has limitations that make it
unsuitable as a long-term solution for direct-attached and network storage applications in the
enterprise: short, bulky ribbon cables that impede airflow and are difficult to install; a large number of
wires and high frequency signals that are prone to electrical interference; and the lack of hot plug
capability. Building on the success of other serial standards (Ethernet, USB, and FireWire), serial ATA
technology is now providing the performance, scalability, and hot plug capability needed for future
generations of storage devices.
HP has actively participated in the Serial ATA (SATA) International Organization (IO) to help develop
specifications that meet the needs of cost-sensitive entry-level to mid-range servers and non-mission
critical network storage. With the introduction of SATA products in 2004, key solution providers like
HP are now offering more scalable and affordable configuration options for a broad range of storage
applications.
This technology brief begins with a description of parallel ATA technology and the reasons for the
industry’s transition to serial I/O technology. Next, it describes how serial ATA technology overcomes
the limitations of parallel ATA. Additional sections describe possible internal and external SATA
topologies.
Parallel ATA technology
Parallel ATA has been the dominant interface for desktop and notebook products since it was
introduced in the 1980's as IDE (Integrated Drive Electronics). The success of parallel ATA in the
desktop and notebook markets is attributed to frequent performance enhancements, backward
compatibility, and a constant goal of driving costs as low as possible.
Figure 1 shows the major components in the parallel ATA architecture. An ATA controller and two
parallel ATA connections are built into the motherboard. Up to two devices can be connected to each
ATA connector in a Master/Slave relationship by using an 80-conductor ribbon cable with three 40-
pin connectors. The bulky cable impedes airflow in the cabinet, which hinders cooling. Cooling is not
a big issue for desktop PC users who rarely install more than one drive.
Figure 1.
Parallel ATA cable with 40-pin connectors for master and slave drives
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