Serial ATA White Paper Introduction This paper provides information about the new serial data interface that is replacing the ATA interface for future storage peripherals such as hard drives and optical disks. WHY SETTLE? The Internet has propelled a whole new generation of data-intensive applications requiring storage architectures that can scale on the fly and remain available all the time. With audio/video streaming, web commerce, and data warehousing applications, to name a few, storage will have to be a scalable network resource that can deliver capacity and data on the fly. However, in today’s world of shrinking IT budgets, many companies are forced to settle for what they can afford. Traditionally, high performance technology was only available to high-level enterprise companies who were willing and able to dig deep into their corporate pockets. But if you’re pockets don’t run as deep, should you really have to settle? Because “It’s ALL About Your Data”, Promise Technology doesn’t believe in settling. Promise Technology, Inc., the originator and global leader in ATA RAID storage solutions is committed to its goal of creating and promoting breakthrough affordable technology that will ensure that you never have to settle again. Promise is dedicated to providing high performance, reliable solutions at attractive price points. That’s why we are pioneering the way for support of cost-effective, high performance Serial ATA architectures by providing highly reliable, mature solutions as Serial ATA products come to market this year.
TRENDS ATA, (Advanced Technology Attachment), has been the main bus since the early days of personal computers. Continued improvements and the relatively low cost of ATA resulted in dominance in the PC The current ATA standard is a parallel meaning that multiple bits of data are transmitted at one time. Advances in high speed networking with the limitations of the current bus architecture have created a bottleneck in today’s networks. This resulted in a shift away from interfaces in favor of serial connections to the disk drive with the associated scalability, reliability, and performance benefits
storage in speed devices market. interface,
coupled parallel has traditional
INTRODUCING SERIAL ATA A side-by-side comparison of a Parallel ATA hard drive (left) Designed to meet the needs of networked storage, and a Serial ATA hard drive (right). SATA (Serial ATA) was created to address the increased data rate demand while at the same time resolving many issues that prevented today’s ATA interface from being widely used in the enterprise. SATA grew out of the need to support growing bandwidth requirements that current Parallel ATA would be unable to maintain in future years. Serial ATA can be referred to as an evolutionary replacement for the SCSI 4– 320MB/sec Parallel ATA physical storage Serial ATA 2– 300MB/sec interface. The new Serial ATA SCSI 3– 160MB/sec Serial A ta is 50% faster architecture introduces a data than Parallel A TA Serial ATA 1– 150MB/sec communication standard for fastParallel ATA/100– 100MB/sec talking drives, which will effectively Parallel ATA/66– 66MB/sec increase bandwidth by 50%, assuring maximum performance. Serial ATA’s point-to-point architecture directly connects each device to the host via a dedicated link. Each device, therefore, has the entire bandwidth dedicated to it, so there is no interaction between devices. Serial ATA eliminates parallel ATA’s master/slave relationship, in which the master device controls the other slave device on the bus, allowing direct communications with any device on the bus. Serial ATA 3– 600MB/sec
Serial ATA architectures only change the physical interface layer. It conforms to the ATAPI (AT Attachment Packet Interface) command set, which is the standard used in today’s ATA drives. It also maintains register and software backward compatibility with Parallel ATA. No device driver changes are necessary and the Serial ATA architecture is transparent to the BIOS and the operating system. This means that Serial ATA is software compatible to parallel ATA drives ensuring a smooth transition from software and driver perspectives, allowing existing applications to work seamlessly with Serial ATA drives. The current Serial ATA specification maps out a 10 year growth plan with three generations of speed enhancements with generation one running at 150 MB/s (to stay ahead of disk data transfer rate and to remove the bottleneck that may occur with 100 MB/s parallel ATA), followed by 300 MB/s and 600 MB/s respectively.
SERIAL ATA FEATURE SET Cabling — Current Parallel ATA cables are bulky, as well as being limited to 18 inches in length. The wide, flat parallel ATA ribbon cables can be difficult to route, and their shape and bulk can restrict air flow inside a chassis or storage enclosure. Serial ATA cables are much smaller and can be up to 1-meter (about 39 inches). The smaller serial cable is easier to route inside the chassis, making them well-suited for storage boxes and high-density server requirements. The smaller diameter cable can also help improve airflow inside the chassis and will facilitate future designs of smaller PC systems.
Serial Transmission — Using 8B/10B Serial transmission to transfer data over the serial cable eliminates crosstalk and other problems that may occur with parallel data transmission. 8B/10B serial transmission is used in numerous technologies including Gigabit Ethernet and Fibre Channel. This encoding data integrity checking is required during high speed data transfer.
Data Robustness — Serial ATA will offer more through checking and error correcting capabilities than are currently available with Parallel ATA. The end-to-end integrity of transferred commands and data can be guaranteed across the serial bus.
Low ASIC Pin Count — Enables ASIC’s to be smaller, which improves cost-effectiveness on both devices and hosts.
Software Compatibility — Serial ATA is compatible at the register level with Parallel ATA. This means Serial ATA requires no existing software and operating systems in order to function, and it provides backward compatibility with existing operating environments. To system software, a Serial ATA device is the same as a legacy ATA device. From a software point of view, this compatibility with legacy hardware ensures an easy transition and faster acceptance.
Hot Plug — Though Promise has long supported hot plug on the Parallel ATA side with its patented Sideband Technology, hot plug has not been part of the ATA specification. Serial ATA allows devices to be hot-plugged and inserted directly into receptacles. The Serial ATA protocol provides the mechanical and electrical features necessary to allow devices to be directly inserted and removed while the system is powered.
THE SERIAL ATA FEATURE SET: MORE BANG FOR YOUR BUCK As you can see, Serial ATA addresses networking issues such as signal integrity, reduced pin count, low voltage, and improved cable and connector plants for smaller form factor drives. Such a feature set will prove to make the Serial ATA technology a viable alternative to SCSI in desktop and server/networked storage markets—all at a fraction of the cost.
WHY USE PROMISE SERIAL ATA Promise’s vision for Serial ATA is that its low cost, high reliability and scalable connectivity will create a vast market for inexpensive networked storage solutions enabling new applications for RAID protected data. As it has in the past, Promise is leading the way so that the advantages of Serial ATA RAID will be fully realized across the whole corporate data set. The Serial ATA specification and architecture align with Promise’s mission of maximizing user return on investment by providing high performance, reliable, and available technology that won’t put a dent in your pocket books.
Promise’s line of Serial ATA products demonstrate a strong commitment to the next generation of powerful, yet inexpensive storage devices for the next generation of PCs and servers, creating low cost storage solutions without compromising performance or reliability, thus leveling the playing fields so that all users have the freedom to compete.
With 14 years of ATA experience, over 10 million ATA ASIC’s shipped in just the last 3 years, and the most mature and reliable ATA RAID Engine in the industry, Promise has long since established itself as the leader of ATA RAID technology. We work closely with virtually every major hard drive manufacturer, tier 1 OEM, and motherboard maker in their ongoing design and test programs, assuring product compatibility and feasibility.
We are committed to promoting products that provide investment protection by reducing the cost and complexity of deploying mission critical storage services. Also, by developing and completely owning our own technology (ASIC, RAID engine, Drivers, and BIOS) Promise has a clear and unobstructed view of the progress being made towards long-term technology development and insight into near-term technology transitions such as Serial ATA.
How did Promise consistently maintain its leadership position in ATA and ATA RAID? Simple—by not only meeting our customers’ expectations but exceeding them. We plan to do the same for Serial ATA. By continuing to push forward the limits of ATA storage performance and reliability, as well as driving the move to Serial ATA architectures that offer performance boosts and greater design freedoms, Promise will continue to provide fast, reliable and economical storage solutions well into the future. How Can I Benefit from Serial ATA? Serial ATA is the next generation personal computer (PC) storage interface. It will replace the Ultra ATA/100 interface used to connect most PCs to their primary storage, which is projected to become a bottleneck within two years. This paper describes the primary benefit of the Serial ATA interface, the increase in data rate. Other features and benefits are also outlined, together with a comparison to alternative storage interfaces. There is a discussion of the current development program, the promoters and the leading role of Maxtor, which now includes the disk drive division of Quantum that was acquired in April, 2001. This introduction to Serial ATA will prepare PC and storage manufacturers to maximize the advantages of this revolution in the personal storage industry. The Need for Change The Advanced Technology Attachment (ATA) interface, previously called Integrated Drive Electronics (IDE), has existed in substantially the same form since 1989, and has become the highest-volume disk drive interface in production. Maxtor, in its role as the patent owner, has led continuous improvements to parallel ATA that extended its data transfer rate from 3.3 Megabytes per second (MB/s) to 100 MB/s, with only one cable change. As PC processor performance has increased, so have the read/write data rates of hard disk drive (HDD) heads and media. This disk rate is projected to exceed today's 100 MB/s interface bandwidth by 2003. Parallel ATA has kept pace in the past, but is nearing its limit, becoming a performance bottleneck. Serial ATA will eliminate this bottleneck by initially offering 150 MB/s and in the future it will provide significant headroom for future improvements. Seven key promoters have worked together to develop Serial ATA: APT, Dell, IBM, Intel, Maxtor, Quantum and Seagate. Of these, Intel has been the leading player on the host side, with Maxtor taking a key role on the device side. All of the promoters are recognized leaders in their respective areas. They are collaborating to leverage their experience with previous interface implementations to ensure that Serial ATA is successfully adopted by the computer industry. A major thrust of the development is to create a cost-effective solution for primary storage. An example of how Maxtor has led this development occurred in October 2000, with Maxtor’s proposed change in the physical layer communication protocol that will provide a
projected overall cost-saving to end-users of $80 million in the year 2003. The original specification called for a transmit and receive frequency tolerance of 150 ppm achievable only by using crystal oscillators costing around $0.50 each. The host already uses these oscillators. Some devices make use of cost-effective ceramic resonators costing around $0.10 each. The tolerance of these parts, however, is as large as 6,000 ppm. The problem for the ceramic resonator is that the specification requires the device to be the first to transmit critical data at a precise clock frequency. The host uses that data to determine the transfer speed, which will enable the support of future generation products. Maxtor recognized the opportunity to provide a lower-cost total solution by redesigning the protocol so that initially the host also provides a constant frequency clock signal, but without data content. The device could then use a ceramic resonator source and phase-lock-loop circuitry to synchronize with and track the host-generated signal. That more accurate source is used to generate the serial clock from the device back to the host. This Maxtor solution has been incorporated into the specification and will enable the Serial ATA system to be more cost effective. In place of the need for two crystal oscillators in a host/device system, only one is called for and the second clock source can be a ceramic resonator, saving $0.40 per system. At an estimate of more than 200 million systems in 2003, that adds up to over $80 million in industry savings! Next Steps Parallel ATA has succeeded as the primary storage interface for the past 10 years. A team of leaders in the PC and storage industries has recognized that this interface is now approaching its limit. This team has leveraged their experience to develop the storage interface for the next 10 years. The Serial ATA interface is optimized for internal primary storage and provides the capability for future enhancements. Serial ATA is designed for low cost, with ease of adoption in mind. Projected next steps for the Serial ATA program are shown below. It is expected that drives and PC motherboards incorporating Serial ATA will be available in 2002. Interface Parallel ATA Universal Serial Bus (USB) IEEE 1394 (FireWire or i.LINK) Serial ATA Target Market INTERNAL storage devices EXTERNAL consumer devices: (printer, scanner keyboard, mouse) EXTERNAL removable storage devices INTERNAL storage devices Cost Low > Parallel > Parallel Requires Royalty = Parallel Speed in Year 2000 (MB/s) 100 1.5 (USB 1.1) 50 N/A Projected Speed in Year 2002 (MB/s) 100 60 (USB 2.0) 50 150 Generation 1 Projected Speed in Year 2005 (MB/s) 100 60 200 300 Generation 2 Cable Length (m) 0.45 6.0 per link 4.5 per link 1.0 OS Driver Support Established parallel USB New 1394 specific Use current parallel Bootable Yes No No Yes Integrated on PC Motherboard Yes Yes No Yes Hot Plug No Yes Yes Yes
Introduction Serial ATA Technology Today’s computers use parallel ATA hard drives, connected by a 40 or 80 pin ribbon cable to an ATA controller. This interface, of course, uses a parallel bus, which is reaching its performance limit with today’s data rates of 100 to 133 MB/sec. Like many legacy interface standards, a parallel bus was easy to implement and provided sufficient bandwidth when originally introduced, but the push to higher data rates is now stressing the capabilities of this bus. In the coming year, Serial ATA drives will be implemented, demonstrating a new standard for hard drive and storage interface that alleviates the performance limits of parallel ATA. In addition to the higher data rates, Serial ATA also provides enhanced features such as hot plug capability, EMI reduction techniques, low voltage signaling and additional power saving features, as well as more sophisticated data handling commands.
The Serial ATA interface replaces today’s 80 pin ribbon cable with a 4 conductor cable. Rather than sending out data in parallel, the data from the controller is serialized, and sent out as a differential signal pair to the target disk device. The disk also sends data on a differential pair back to the host controller. Simultaneous transmission occurs on both channels, from host to disk and disk to host. Because of this, Serial ATA is a point-topoint link, and only supports a single device per controller interface, in contrast to the primary and secondary support of two drives from a single parallel ATA port. Controllers can address multiple devices, but each device requires a separate, dedicated port. There are many benefits of the smaller cabling from the overall system perspective of a PC manufacturer. The flat, wide ribbon cables are restrictive to air flow within the PC enclosure, and often require complex folding and assembly to support the devices used today. With the thinner cable of Serial ATA, airflow restrictions are minimized and thermal design issues are more easily resolved, as seen in Figure 1. The initial data rate for Serial ATA is 150 MB/sec of data transfer, requiring a wire speed of 1.5 GHz for serial data transmission. The specification, published by the Serial ATA Working Group in August 2001, also calls for second and third generation data rates, which double to 300 MB/sec and then 600 MB/sec, (with wire speeds of 3.0 Gbps and 6.0 Gbps) respectively. In serializing the data, standard 8b/10b encoding is used and techniques such as spread spectrum clocking and data scrambling to minimize repetitive patterns are used to reduce EMI. Serial ATA is also more compatible with the shrinking feature sizes and power levels used in today’s complex interface chips. Serial ATA, with it’s differential signaling technique uses only a 250mV swing in it’s data transmission, versus 3.3V or even 5V for the parallel ATA interface. In today’s PCs, the southbridge chip provides an integrated hard drive controller. This controller has two ports, a primary and secondary, and each port can support two drives, a primary drive and a secondary drive. Thus a total of four ATA based devices can be connected – typically a bootable hard disk drive, and one or more optical devices such as a CD-ROM, CD-RW or DVD disk. For support of additional drives, typically the PCI interface is used, and PCI based ATA controllers can be added to provide connectivity for additional disks that might be required. An example of this configuration is shown in Figure 2. Initial support of Serial ATA devices will be provided through a PCI based controller: This can be installed on a motherboard directly, or provided through an add in card connected to the PCI slot on a motherboard. With a 32 bit PCI bus, a data rate of 33 MHz
allows up to 133 MB/sec of data transfer, and a data rate of 66 MHz would allow 266 MB/sec. This would provide sufficient bandwidth for a 2 port Serial ATA controller, because the sustained transfer rate would be roughly 100 MB/sec. For enterprise storage systems, such as external RAID devices, more ports would be ideal – 4, 6 or even 8 ports might be desired. In this case, a PCI-X interface would be better matched in terms of bus bandwidth. Today, we are already seeing parallel ATA RAID systems being implemented, because a SCSI based solution is significantly more costly. With the enhanced features of Serial ATA, an even more robust and flexible RAID system can be developed. Enhancements to the current Serial ATA specification designed specifically to address these market requirements are being developed by the Serial ATAII working group and will be released later this year. The Serial ATA protocol is defined as three different layers: •
The transport layer, which interfaces to higher order protocols such as PCI or Parallel ATA. The transport layer is responsible for interfacing to the ATA register file, interpreting commands, and giving the link layer blocked tasks.
•
The Link layer is responsible for packet framing, the 8b/10b encoding and decoding and generating and checking the CRC codes. The link layer also handles flow control, buffering data and primitives as needed to accommodate burst transfers, and data rate variations from spread spectrum clock use.
•
The Phy layer has the 10b encoded data from the Link layer passed to it, where the data is serialized and sent out over the cable and connector. The Phy layer also is responsible for deserializing the data received from the other end of the link and interpreting out of band signaling used for power up and hot plug detect.
The hierarchy of these three layers is shown in Figure 3.
With an appropriate transport layer, it is possible to make a “bridge” chip which can accept Parallel ATA commands, and convert them to Serial ATA data. These chips can enable an easy system conversion to Serial ATA, because all PC’s already incorporate parallel ATA controllers. Most of the initial hard disk drives will also utilize these bridge chips, thus enabling parallel ATA drives to work with Serial ATA cabling. An example of this configuration is shown in Figure 4. Although these approaches will work well as enabling technology on the drive side, there are some issues with this implementation that make it less desirable than integrated controllers on the host side. First, with a bridge chip, the parallel ATA interface side will be limited to 100 or 133 Mbytes/sec, because that is the speed of the parallel ATA controllers. Second, with a bridge chip on the host device, the software driver can only control the parallel ATA controller, and can’t access the Serial ATA register space. For an integrated controller, access to this register space allows more robust error handling, and more flexible data transmission. Finally, most bridge chips take in one parallel ATA interface and have one serial ATA output. Because a standard parallel ATA port could support two disk drives (primary and secondary), use of a single port bridge chip reduces the number of devices that could be connected. At some point, the southbridge will incorporate the Serial ATA technology as a replacement for the parallel ATA currently supported. There are two possible approaches for this integration. Full integration of the Serial ATA transport, link and Phy layers would enable direct serial connection from the southbridge chip. A challenge with the full integration lies in incorporating the high speed analog blocks of the Phy layer with the extensive digital logic in the southbridge. For many other high speed serial interfaces, the convention has been to keep these chips, such as networking interfaces, as discrete chips. A similar convention is found with high speed digital display interfaces used with external Phy chips rather than integration into the northbridge graphics block.
The alternative integration path, where the digital blocks of the transport and link layers are incorporated into the southbridge, while supporting an external Phy layer, is more compatible with the architecture used today. This alternative path is shown in Figure 5 It is even possible to build a controller which could MUX a PATA port with a SATA link to Phy interface, providing flexibility in implementation without increasing pin count. The use of an external Phy chip also provides an easier path to the second generation speeds of 3.0 Gbps, and avoids the yield impact and design problems during die or process shrinks. Because the hard disk drives are the only ATA devices pushing the data speeds needed for serial ATA, the driving force for ATAPI devices to move to Serial ATA is not very strong. Thus it is expected that most controllers will first convert only one of their ports from parallel to serial ATA, leaving a legacy parallel port for connection to optical drives. Over time, as optical devices also evolve, it is expected that a full conversion of parallel to serial ATA interfaces will occur in the chipset.
Summary: As seen from the examples outlined above, there are a number of implementation approaches to enable Serial ATA functionality. A summary of the time frames, relative costs and advantages and disadvantages of each approach is shown in Table 1. One merit of a PCI-based integrated controller is that it can be adopted into most PC platforms without requiring any additional changes. A bridge-based solution is also possible, although this solution is not as robust and could also be more costly than the integrated controller if multiple chips are used. The lower cost approach of southbridge chipset integration requires a substantial change in the chipset architecture, particularly if the Phy layer is incorporated. With an external Phy, the digital logic needed for the link and transport layers are more readily incorporated, so the barrier for implementation is not as large. It is expected that in the initial phase of Serial ATA adoption, integrated PCI based controllers will predominate, to be supplemented by integrated chipset capability over the following year.
Resources and Call to Action Call to Action:
System and device manufacturers should begin preparing now for the implementation of Serial ATA in their platforms. Both host controllers and disk drives enabled with Serial ATA will be available this year, and rapid adoption is expected over the next year. Numerous advantages of Serial ATA over parallel ATA are enabled, including higher data rates, lower power consumption, reduced EMI, and enhanced features such as hot plug capability. This will allow Serial ATA to be employed not only in desktop PCs and workstations, but in enterprise storage applications as well. Feedback:
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To provide feedback about this white paper, please send e-mail to
[email protected]
For More Information:
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For more information about Serial ATA, see the Serial ATA Working Group web site, available at: http://www.serialata.org/
Acronyms and Terms ATA – AT Attachment ATAPI – ATA Packet Interface CD-ROM – Compact Disk – Read Only Media
CD – RW - Compact Disk – Read/Write CRC – Cyclic Redundancy Check DVD – Digital Versatile Disk EMI – Electromagnetic Interference MUX – multiplexer PCI – Peripheral Component Interconnect RAID – Redundant Array of Inexpensive Disks SATA – Serial ATA SCSI – Small Component System Interface
Figures and Tables This section includes the figures and tables referenced in this paper.
Figure 1:
Parallel ATA Cabling
Serial ATA Cabling
Figure 2:
Figure 3:
Figure 4:
Figure 5:
Q1 A1
What is Serial ATA? Serial ATA is a disk-interface technology developed by a group of the industry's leading vendors to replace parallel ATA. The group is known as the Serial ATA Working Group. The Serial ATA 1.0 specification was released in August 2001.
Q2
What are the compelling reasons why Serial ATA is a viable option for server and NAS networked storage? 1) Scalability — Serial ATA is a point-to-point connection and allows multiple ports to be aggregated into a single controller that is typically located either on the motherboard or as an add-in, RAID card. Through backplanes and external enclosures, Serial ATA will be deployed in high-capacity server and networked-storage environments.
A2
2) Price — Serial ATA was created, with desktop prices in mind, as a replacement for Parallel ATA. Initial hard disk drives (HDD's) are expected to be priced competitively for the desktop. With the scalable features of Serial ATA combined with desktop price-points, greater storage capacity may be realized at a lower total solution cost than with traditional server and networked storage.
3) Cabling — Serial ATA specifies a thin, point-to-point connection which allows for easy cable routing within a system. This avoids master/slave, "daisy-chaining", and termination issues. Also, better airflow can be realized compared to systems with wider ribbon cables. 3) Performance — Serial ATA technology will deliver 1.5 Gbps (150 MB/sec) of performance to each drive within a disk drive array. Q3 A3
When will Serial ATA infrastructure products be shipping in volume? Individual vendors will best be able to advise on product plans. However, hard disk drives, cables, enclosures, and controllers are expected to be available to OEM and channel customers in 2002, with enterprise system vendors shipping platforms with Serial ATA storage by the second half of the year.
Q4 A4
Where is Serial ATA positioned relative to other interface technologies? Serial ATA technology provides a new serial interconnect designed to change the way vendors develop storage systems. The first deployments, where price is an important issue, are intended for entry-level servers and network-attached storage. As the infrastructure continues to develop, Serial ATA will penetrate into higher-end servers and more complex storage systems.
Q5 A5
What is the long-term road map for Serial ATA? Serial ATA defines a roadmap starting at 1.5 gigabits per second (equivalent to a data rate of 150MB/s) and migrating to 3.0 gigabits per second (300 MB/s), then to 6.0 gigabits per second (600 MB/s). This roadmap supports up to 10 years of storage evolution, based on historical trends.
Q6 A6
How does Serial ATA handle backward compatibility issues? Serial ATA supports legacy drivers for Parallel ATA. OEMs can deploy Serial ATA, today, using existing parallel ATA drivers. Vendors intend to supply bridges for parallel-to-serial conversion for legacy devices.
Q7 A7
Are there any known interoperability issues with Serial ATA? One of the primary requirements of the Serial ATA 1.0 specification was to maintain backward compatibility with existing operating system drivers to eliminate incompatibility issues.
Q8 A8
How will operating systems handle Serial ATA? Because of the legacy support inherent in the specification, operating support will be simplified. The Serial ATA specification allows for additional features to be added to applications. Additional features will be subject to normal driver validation processes.
Q9
How does the end-user benefit from using Serial ATA technology in servers and NAS? The end-user will benefit from lower cost, higher performance (via increased speed and scalability), and easier configuration. Serial ATA allows for higher performance while using existing, proven features such as 3.5" disk drives. Configuration of Serial ATA devices will eliminate many of today's requirements for jumpers and settings.
A9
Q10 How does the system vendor benefit from using Serial ATA technology in servers and NAS? A10 Benefits for the OEM:
• • • •
Easier configuration and design with cables that are thinner, have smaller connectors, and are simpler to route and install Ability to use HDD technology across multiple segments such as desktops, entry and midrange servers, and networked storage Easier training for Sales and Tech Support staff Improved silicon design with lower voltage that will ease current design requirements in Parallel ATA
Compatibility with today's software that will enable Serial ATA to run on the new architecture without modification Q11 How can I get more information? A11 More information can be obtained at this Web site and the Serial ATA Working Group official web site. Q12 What is Intel's role in Serial ATA and storage? A12 Intel® has been a leading force, and it is one of over 80 companies driving the Serial ATA initiative to enable low cost, high-performance, next-generation disk interconnects. As a leading supplier of storage building blocks, including Intel® Architecture processors, motherboards, I/O processors, ethernet NICs, RAID controllers, and iSCSI HBAs, Intel® sees Serial ATA as a critical technology for next-generation storage platforms. Serial ATA - The Future Interface for High Performance and Mainstream Desktop PCs Most desktop storage systems today use a parallel bus interface referred to as Ultra ATA/100. The parallel ATA interface has been in use on desktop systems as the mainstream internal storage inter-connect, since the 1980's (over 15 years!). Today's PCs demand higher speeds, more robust data integrity and flexibility for innovative smaller designs. Physically and electrically, the current parallel bus has run into limitations that will prevent this bus from providing higher speeds of data transfers. The move to a new technology is inevitable in the eyes of industry leaders such as Intel, Dell, Seagate, Maxtor and APT.
These same leaders formed the SerialATA.org and are highly dedicated to bringing this new technology to the forefront of today's PCs. Serial ATA is designed to overcome the limitations of parallel ATA while providing scalability for years to come. Setting the goal to be compatible and at cost parity with current parallel ATA drives when in volume, the SerialATA organization is promoting the adoption of Serial ATA in all systems where ATA drives are being used today. What is Serial ATA? Serial ATA is a "serial" architecture as opposed to today's "parallel" ATA internal disc drive bus. Serial ATA wraps many bits of data into a packet and then at a higher speed (up to 50% higher) than parallel, transfers the packet of data down the wire to or from the host. Today Cyclic Redundancy Checking (CRC) is performed on the data being transmitted back and forth but not on the commands. Serial ATA integrates CRC on the command and data packet level for enhanced bus reliability. Cyclic redundancy code detects all single and double-bit errors and ensures detection of 99.998% of all possible errors. A Serial ATA drive can transfer data at 150MB/sec on the bus to the host system with extremely reliable accuracy and the Serial ATA interface will continue to allow scalability for a very long time. Serial ATA provides expansion for reliable performance growth Generation 1
Generation 2
Generation 3
Approximate Data Rate
150 MB/sec
300MB/sec
600MB/sec
Approximate Bus Speed
1.5GB/sec
3GB/sec
6GB/sec
Approximate Introduction
Fall of '02
Mid'04
Mid'07
Additional Benefits In addition to a faster, more reliable bus, Serial ATA improves cabling and connectors for a robust yet simpler integration. Gone are the days of bent pins and clumsy cabling and needless returned hard drives. Serial ATA cables are thinner and longer for improved system airflow and innovative system designs such as small form factor and consumer electronic boxes. Connectors are easier to snap into place without any pins but rather a blind-mate type of connection. Without the wide cables, system integrators can easily route the longer data cables (1 meter) within the system for simplicity or innovative designs. Seagate Technology, A Native in Serial ATA Still in its early market entry stage, Serial ATA provides immediate benefits to desktop users. Serial ATA, an innovative new interface, allows continued performance growth, enhanced data reliability, and overall improved system dynamics above and beyond what Parallel can efficiently continue to provide. A true "Native" Serial ATA solution offers customers the "Real McCoy" in Serial ATA technology. By implementing Serial ATA technology, not only on the physical layer of the drive, but also in the ATA controller link and transport layers, Seagate drives can communicate from the drive to the host directly up to the full 150MB/sec speed on the bus. In addition, the native solution incorporates command queueing, which can be a big performance boost in operating systems that can take advantage of that type of function. Some drive manufacturers may not immediately offer these "native" Serial ATA features on their 1st generation Serial ATA drives due to the difficulty of this integration. Native Serial ATA = 150MB/sec bus speed, command queueing support, super-set feature ready (first party DMA) -A True Serial ATA Controller, Not Just A Translator. There is another way to quickly integrate Serial ATA onto a drive and it's referred to as a "bridge" solution. In a bridged solution, the drive manufacturer inserts a data serializer/deserializer function before the data is sent or received by the on board ATA controller. Data on a bridged SATA solution can only be sent or received as fast as the ATA controller works. Since the serial functionality is not natively tied to the drive controller link and transport layers but rather a separate function that translates data for a parallel controller, it can only transfer at that speed (100 or 133MB/sec). The industry is more than ready to adopt Serial ATA technology and Seagate is proud to offer their customers a high performance "true native" Serial ATA solution. Look for controller cards and drives in the Fall of 2002 and motherboards with Serial ATA ports integrated in mid 2003.