SATA Interface

SATA Interface

SATA is an acronym for Serial ATA, which is Serial ATA. It is a computer bus and its main function is to serve as a data transfer between the motherboard and a large number of storage devices (such as hard disks and optical disk drives). This is a new type of hard disk interface that is completely different from serial PATA and is named after serial data transmission. SATA bus uses embedded clock signal and has stronger error correction ability. Its biggest difference compared with the past is that it can check transmission instructions (not only data), if it finds errors, it will be corrected automatically. This is very large. To improve the reliability of data transmission. The serial interface also has the advantages of simple structure and hot swapping.
Developed in November 2000 by the "Serial ATA Working Group" group, SATA has completely replaced the old hard disk drive of the old PATA (Parallel ATA or formerly known as IDE) interface, and is named after the serial data transmission. In terms of data transmission, SATA is faster than ever and supports hot-plugging so that the computer can be plugged in or unplugged during operation. On the other hand, the SATA bus uses an embedded clock frequency signal, which has stronger error correction capabilities than ever before. It can inspect transmission instructions (not only data), automatically correct if errors are found, and improve the reliability of data transmission. Sex. However, the most obvious difference between SATA and the past is the use of thinner cables to facilitate the air circulation inside the chassis, which has increased the stability of the entire platform to some extent.
At present, SATA has three specifications: SATA 1.5Gbit/s, SATA 3Gbit/s, and SATA 6Gbit/s. There will be faster SATA Express specifications in the future.

Principle Advantages

Compared with Parallel ATA, SATA has a big advantage.
First, Serial ATA transmits data in a continuous serial fashion, which can increase the bandwidth of data transmission using a higher operating frequency with fewer bit widths. Serial ATA will only transmit one bit of data at a time. This will reduce the number of pins on the SATA interface, making the number of connecting cables smaller and the efficiency even higher. In fact, Serial ATA can do all the work with only four pins for connecting cables, connecting grounds, sending data, and receiving data. This architecture also reduces system power consumption and system complexity.
Secondly, Serial ATA has a higher starting point and greater development potential. Serial ATA 1.0 defines a data transfer rate of up to 150MB/sec, which is 133MB/sec higher than the fastest parallel ATA (ie, ATA/133). The data transfer rate is still high, and the data transfer rate of the released Serial ATA 2.0 will reach 300MB/sec. Ultimately, Serial ATA 3.0 will achieve the highest data transfer rate of 600MB/sec.

SATA Interface Architecture

In combination with the SATA 2.5 protocol standard, the SATA interface is divided into four levels to implement: physical layer, link layer, transport layer, and application layer.  For example, SAS interface architecture diagram.

SATA Interface Physical Characteristics

The SATA interface is a new type of computer hard disk interface. In terms of the physical characteristics of the interface, it completely overturns the SATA parallel interface model. The interface is divided into two parts: signal and power. For example, the SATA physical interface
SATA physical interface
SATA physical interface diagram [2]
(a) is the connector for the signal portion of the hard disk device, (b) is the power supply to the device, and (c) (d) is the signal and power connector for the cable portion respectively, and (e) is the cable connector for the host portion, ( f) and (g) are schematic diagrams of cable and socket connections.
The signal portion of the serial SATA interface is composed of 7 cables. Three of them can weaken the interference between the serial cables. The other four are two-differential signal lines, which transmit and receive signals respectively.
The role. There are 15 cables in the power supply section, each providing 3.3V.
Cable pin assignment
Cable pin assignment map [2]
5V, 12V power supply. For example, the cable pin assignment map.

Compatibility

The Serial ATA specification is not only based on the future, but also retains a variety of backward compatibility, there is no compatibility problem in use. On the hardware side, the Serial ATA standard allows the use of a converter to provide compatibility with parallel devices. The converter can convert parallel ATA signals from the motherboard to serial signals that can be used by Serial ATA hard drives. There have been many such transfers. The card/adapters are on the market, which protects our original investment to a certain extent and reduces the upgrade cost. On the software side, Serial ATA and Parallel ATA maintain software compatibility, which means that manufacturers do not have to use them at all. Serial ATA rewrites any driver and operating system code.
In addition, the Serial ATA cabling is much simpler than the traditional Parallel ATA (Parallel ATA) cabling and is easily retractable, providing significant improvements in airflow and heat dissipation within the enclosure. What's more, SATA drives are different from parallel ATAs, which are always trapped inside the chassis. They are highly expandable and can be externally mounted.
SATA interface
SATA interface (6 photos)
The cabinet (JBOD) can not only provide better heat dissipation and plugging and unplugging functions, but also can be multi-connected to prevent single points of failure. Because the design of SATA and Fibre Channel is exactly the same, the transmission speed can be guaranteed by different channels. Server and network storage are important.

Driver

The External Serial ATA abbreviation is an extension of Serial ATA 1.0a for external drives. Although the scale is relatively small, corresponding products have already been circulated in the market.
In order to prevent misconnection, the shape of the eSATA interface is different from that of the SATA interface. The maximum length of the connecting line is 2m. Hot swappable. Transmission speed can reach more than 2 times of the mainstream USB2.0 transmission speed.

Standard Specification

The emergence of the SATA standard has caused a great stir in the computer storage industry. In addition to changing the parallel transmission method in the past, the serial method has not only effectively reduced the size of the cable, but also achieved speed in transmission. Considerable improvement.
SATA standard changes
In fact, the name of the SATA II that we commonly find is the name of a committee. The purpose of the committee was to establish the earliest SATA 1.x standard. Later the organization was renamed SATA International (SATA-IO). However, the name of SATA II has been retained. Due to different functionalities or support levels for different products introduced by different vendors, there are differences in the naming conventions of various SATA products.
Because SATA-IO does not rigidly specify the naming rules and functional requirements, it has also caused many product positioning problems in the initial stage of promotion. Generally speaking, general manufacturers use more specific functions as their naming rules. Most common ones are based on their maximum transmission speeds. The common names of SATA 300, SATA 3Gb/s, and SATA 3G are partially accessed by SATA II. After supporting the specification name, its products are quite complete in terms of hardware specifications, so most of them abandoned the past speed naming rules. In addition, SATA-IO will be identified by various manufacturers in the IDF exhibition at the end of August 2005. SATA II content such as 3Gbps, Local Command Queuing (NCQ), Port Multipliers, and port selectors were consolidated into the SATA 2.5 standard specification, significantly reducing market disruptions. In the first quarter of 2007, SATA-IO introduced the 2.6 version of the specification, and further version 3.0 specifications will also be introduced in the second half of the year.
The advantages of SATA still have to face
The emergence of SATA 1.0 represents that the computer industry formally transitions from low clock speeds to high clock speeds. The initial specification is set at 1.5 Gbps, which obviously has more abundant transmission energy than the previous IDE interface. However, although SATA provides such a wide range of buses, the speed of hard disk drives has progressed very slowly, and the speed and speed of disk density have not increased fast enough, so that the increase in the speed of the SATA bus is of little significance.
SATA has become a universal storage interface standard
An example loved by many people: riding a 50cc lamb motorbike on a speed limit of 200 freeways is just enough to describe the hard drive situation. According to the SATA 1.0 specification, the maximum transmission speed is about 150 Mbyte/s, and even if the high-end SATA hard disk is up to 10,000 rpm or more, the continuous transmission speed cannot exceed 100 MByte/s. The high bus bandwidth of SATA is expected to be brought into play. Therefore, it is necessary to use disk arrays to have a solution. Another method that can take advantage of the high bandwidth of the SATA interface is to use a hard disk external device with a linker to share the bandwidth of a single SATA port evenly. The use of hard disks means, in terms of a single hard disk, that the transmission speed will not be greater than in the past in the IDE interface.
Difference between eSATA connector and SATA connector

ESATA and SATA interfaces
Secondly, although SATA has hot-pluggable specifications, most of the connecting cables are designed for use with internal hard disks. The maximum number of plug-in cables is only about 200 times. Exceeding the number of plugs and plugs, the cable connector will be degraded. It may cause damage to the hard disk. Even for eSTAT cables for external applications, the number of plug-ins is still only about 2,500 times, which is far from the USB interface, but this involves the connection between cable material and cost. Although theoretically higher insertion and removal times can be achieved, it is also crucial that the price is acceptable to consumers. While SATA cables have an advantage in width, the length is limited to within 2 meters, which is a considerable limitation for some applications, but this can be solved by xSATA.

Enhancements to the SATA 2.6 specification

The technology added in SATA version 2.6 is mainly for small-scale embedded storage or mobile applications. These technical contents include the following items:
1. The built-in daughter card cable and connector for installing the SATA optical drive into a small device such as a small form factor.
2. The 1.8-inch hard drive can be mounted to a mini-SATA connector such as a UMPC.
3. Since there are miniature connector specifications, it is natural to design built-in or external multi-channel cables and connectors for such miniature           connectors.
4. The strengthening of NCQ priority allows data to be dynamically assigned priority levels for data transmission under complex loading conditions to avoid  congestion.
5. The laptop may be turned off or not using the NCQ function to avoid system performance if the driver is incomplete.
The following figure shows the miniaturized connection interface developed by SATA 2.6. (SATA-IO)

SATA 2.6 is enhanced for mobile applications

From the above points, we can see that the SATA 2.6 version is mainly aimed at smaller applications, such as samll form factor or internal and external specifications such as UMPC. However, in such applications, the number of storage devices is limited. And the speed of the storage device itself will be affected by different factors such as the speed (for example, the 1.8-inch hard disk commonly used in UMPCs has a maximum transfer speed of about 20 MByte/s, which is less than one-third of that of the conventional 3.5-inch drive). The import does not seem to be necessary. The UMPC itself is also not capable of supporting disk arrays. The only application that may use SATA power is connecting multiple external storage devices using a linker.
The shortcomings of traditional mechanical hard disks are at a glance on UMPCs. They not only consume large amounts of power, they are slow, and their capacity growth is not fast. Therefore, the sudden emergence of solid-state drives (SSDs) may become a boost for SATA bandwidth promotion. However, from another perspective, UMPC may also have built-in Express Card interface. Compared with SATA, Express Card has an advantage over SATA in terms of specifications, speed, and connection. In the next two or three years, the price and capacity of SSDs will still be unacceptable to the average consumer. Traditional micro hard drives still have room for survival. Therefore, the competition between SATA and Express Cards in this area is still undecided.

The next stage of SATA 3.0

The biggest improvement of SATA 3.0 is to increase the maximum transmission bandwidth of the bus to a spectrum of 6Gbps, which has greatly increased the application space for linking shareware and connectors, and it has been applied to external applications that require large-capacity and high-speed transmission. Can play its strengths. The connection test with better patience is also underway, but as of now, its detailed content is not yet clear, but with its huge bandwidth now, it actually exceeds the scope of general consumer applications, and focuses on For specific professional applications, the market is much smaller.
Mechanical hard drives will continue to exist for a long period of time in the future, and the increase in transmission speed will also maintain the current range. Therefore, hardware manufacturers must develop more and more different connection methods in order to effectively consume these huge amounts. The bandwidth allows consumers to feel the benefits of digital growth more directly, instead of focusing on the written specifications and not giving users the benefit of related applications.

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