SATA CABLE

SATA
SATA (Serial Advanced Technology Attachment) is an industry-standard serial hardware driver interface and is a hard disk interface specification jointly proposed by Intel, IBM, Dell, APT, Maxtor, and Seagate Corporation. In 2001, the Serial ATA committee, consisting of Intel, APT, Dell, IBM, Seagate, and Maxtor, formally established the Serial ATA 1.0 specification. At the IDF Fall conference, Seagate announced the Serial ATA 1.0 standard. Announced the establishment of the SATA specification.

Chinese name: Serial Advanced Technology Attachment         Abbreviation: SATA

Foreign Name: Serial Advanced Technology Attachment         Application area: Computer

SOURCE
Although serial ATA related equipment was not yet officially listed in 2002, the Serial ATA committee has preliminarily established the Serial ATA 1.0 specification. The SATA specification increases the theoretical external transfer rate of the hard disk to 150MB/s, which is 50% higher than the PATA standard ATA/100 and about 13% higher than the ATA/133. With the development of future versions, the SATA interface The rate can also be extended to 2X and 4X (300MB/s and 600MB/s). From its development plan, the future SATA will also increase the interface transfer rate by increasing the clock frequency, so that the hard disk can also be overclocked.

CLASSIFICATION
The SATA interface needs the support of hardware chips, such as Intel ICH5(R), VIA VT8237, nVIDIA's MCP RAID and SiS964. If the motherboard south bridge chip can not directly support it, you need to select a third-party chip, such as Silicon Image 3112A chip, etc. However, this will also produce some differences in hardware performance, and drivers are also more complicated.

SATA advantage
The serial interface has a simple structure, supports hot swap, high transmission speed, and high execution efficiency. The hard disk that uses SATA (Serial ATA) port, also called serial hard disk, is the trend of future PC hard disks. Serial ATA uses a serial connection method. The serial ATA bus uses an embedded clock signal and has a stronger error correction capability. The biggest difference compared to the past is the ability to check transmission instructions (not just data). Finding errors is automatically corrected, which greatly improves the reliability of data transmission.
A serial hard disk is a new type of hard disk interface that is completely different from parallel ATA and is known for its serial data transmission. Compared with Parallel ATA, there are many advantages. First, Serial ATA transmits data serially, sending only one bit at a time. This will reduce the number of pins on the SATA interface, which will reduce the number of connected cables and increase the efficiency. In fact, Serial ATA can do all the work with only four pins, which are used to connect power, connect ground, send data, and receive data. At the same time, this architecture can also reduce system power consumption and system complexity. Secondly, Serial ATA has a higher starting point and more potential for development. Serial ATA 1.0 defines a data transfer rate of 150MB/s, which is the highest data rate that can reach 133MB/s than the fastest parallel ATA (ie, ATA/133). The transmission rate is still high, and the data transfer rate in Serial ATA 2.0 reaches 300MB/s, and finally SATA will achieve the highest data transfer rate of 600MB/s.
The physical design of SATA can be said to be based on Fibre Channel (fiber channel) as the blueprint, so the use of four-wire; demand voltage is significantly reduced to 250mV (up to 500mV), compared to 5V of the traditional parallel ATA interface is less than 20 times! Therefore, manufacturers can attach Serial ATA hard disks with advanced hard disk functions such as Hot Swapping. More importantly, in connection form, in addition to the traditional point-to-point form, SATA also supports “star” connection, which can provide design convenience for advanced applications such as RAID; in practice In use, the SATA host bus adapter (HBA, Host Bus Adapter) is like a switch on a network, and can communicate with each hard disk in the form of a channel, that is, each SATA hard disk has a single transmission channel. There is no master/slave control problem like Parallel ATA.

PROSPECT
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 ATA 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 pick-up cards/adapters are listed, which protects the 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 vendors do not need to use Serial. ATA overrides 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. Moreover, SATA HDDs are different from Parallel ATAs, which are always trapped inside the chassis. They are highly expandable and can be externally mounted. External cabinets (JBOD) not only provide better heat dissipation and plug-in functions, but also can be multiplexed. The connection is to prevent single point of failure; because the design of SATA and Fibre Channel is exactly the same, the transmission speed can be guaranteed by different channels, which is of great significance in server and network storage.
Serial ATA has many advantages over parallel ATA and will become a cheap alternative to parallel ATA. And the transition from Parallel ATA to Serial ATA is also a general trend and should only be a matter of time. Related vendors are also promoting SATA interfaces, such as Intel's ICH6 series of South Bridge chips compared to the ICH5 series of South Bridge chips, the number of supported SATA interfaces has been increased from 2 to 4, and the parallel ATA interface has been reduced from 2 to 1. nVidia's nForce4 series chipsets already support SATA II, Serial ATA 2.0, and Samsung has adopted the Marvell 88i6525 SOC chip to develop a new generation of SATA II interface hard disks, which was introduced in early 2005.
In 2007, the SATA2 and SATA 2.5 standards were developed and the speed reached 3000Mbps (theoretically equivalent to 375MB/s).

Extension specifications
Since Intel introduced the SATA 1.5Gbps South Bridge chip (ICH5) in the second quarter of 2003, the SATA interface has replaced the traditional PATA (Parallel ATA). In addition, SATA is more outstanding in terms of performance and functionality than USB and IEEE 1394, which are currently on PCs. However, after one year of market baptism, the original SATA 1.0/1.0a (1.5Gbps) specification encountered some problems. In 2005, SATA hard drives entered a new stage of development. The performance and configuration of higher SATA 2.0 products have already appeared in the market, and the arrival of these high-performance SATA 2.0 hard drives has undoubtedly accelerated the change of the hard disk market.

Development path
SATA was introduced by Intel Corporation at the IDF2000 conference. This technology allows users to have high-performance hard drives without sacrificing the integrity of the data. The biggest advantage of SATA is its high transmission rate. The working principle of SATA is very simple: use the serial serial way to realize the data transmission to obtain the higher transmission rate. In 2003, the SATA1.0 specification released a transfer rate of 150MB/s, which is not only higher than the 100MB/s (ATA100) provided by ordinary IDE hard disks, but even exceeds the maximum transfer rate of 133MB/s (ATA133).
SATA has also greatly improved its data reliability. SATA can perform a cyclic redundancy check (CRC) on both command and data packets. Not only can it detect all single-bit and double-bit errors, but it can also detect 99.998% of possible errors based on statistical principles. In contrast, PATA can only verify the data transmitted back and forth, and can not verify the instructions, coupled with large interference at high frequencies, so the stability of data transmission is poor.
In addition to transmission speed and more reliable data transmission, space saving is the most attractive aspect of SATA, which is more conducive to heat dissipation inside the chassis. Crosstalk between cables is also effectively controlled. However, there are many shortcomings in the SATA 1.0 specification, especially the lack of support for some of the advanced features required for server and network storage applications. For example, in a typical multitasking, multi-request server environment, SATA1.0 hard disks do suffer from significant performance degradation, poor maintainability, and poor connectivity. At this time, the emergence of SATA 2.0 has been well supplemented in this regard.

SATA II
3Gb/s transmission rate
In the SATA 2.0 extension specification, 3Gb/s is mentioned the highest frequency. Since SATA uses 8bit/10bit encoding, 3Gb/s is equivalent to an interface speed of 300MB/s. However, from a performance point of view, 3Gb/s does not bring much improvement. Even in the case of RAID applications, the performance increase is not as large as expected. Because the internal transfer rate of the hard disk does not reach the same level as the interface speed, and the impact of the interface speed is not very great, in most applications, the hard disk spends more time on seeking instead of transmitting. The increase in the interface rate directly affects the operation of reading and writing from the cache. Therefore, in theory, large cached products will receive greater benefits from 3Gb/s. From the current situation, it is believed that the speed of 3Gb/s adoption will accelerate, but the market will still have a coexistence period of 1.5Gb/s and 3Gb/s.
Principle of PATA CRC, PATA only performs CRC check on data part
Supports NCQ technology
Description of NCQ
Description of NCQ
Among the new series of functions brought by the SATA 2.0 extension specification, NCQ (Native Command Queuing) is the most interesting feature. The hard disk is an electromechanical device and is easily affected by the inertia of the internal mechanical components. The rotational waiting time and the seek waiting time greatly limit the efficiency of the hard disk for data access and retrieval.
Specifically, if the head stops above the target track and misses the initial LBA (Logical Block Addressing), a rotation wait time will occur. In the worst case, the hard disk will take a full rotation to access the starting LBA before continuing to read data from the remaining target LBAs. If the LBA is randomly distributed with respect to the head angular position, the average rotation waiting time is half of the maximum rotation waiting time. The seek wait time is the time taken for the read/write head to be accurately positioned above the track of the storage target LBA. For example, when performing a single read command, the head only needs to access one track, but if there are multiple commands to be executed, the hard disk has to access all the target LBAs, which takes a lot of time.
If intelligent internal management is performed on the execution of this mechanical action of the hard disk, the efficiency of the entire workflow can be greatly improved. That is, the commands in the queue are fetched and then reordered so as to efficiently acquire and send the data requested by the host. At the same time when the hard disk executes a certain command, new commands may be added to the queue and are queued for the job to be executed. If the new command happens to be the most mechanically efficient, then it is the next command to be processed in the queue. However, an effective sorting algorithm considers both the linear position and the angular position of the target data, and also optimizes the linear position and angular position to minimize the service time of the bus. This process is also called "based on seek and rotation. Optimized order reordering."
Desktop PATA hard disk queues have been strictly limited to a depth of 32 levels. If you increase the queue depth, it may be counterproductive - increase the risk of command accumulation. Usually PATA hard disk receives the order when there are two kinds of choices: First, execute the order immediately, second, delay the execution. For the latter case, the hard disk must notify the host when the command is executed by setting the attention flag and Service bit. However, the hard disk cannot actively communicate with the host. This requires the host to periodically poll all the hard disk sectors periodically and find the Service bit. A service command is issued to obtain from the hard disk which execution command to execute. Furthermore, the Service bit does not contain any identification information for the command to be executed. The necessary command identification information is transmitted in the form of a tag value together with the data request, and is only used by the host to set the DMA engine and receive data buffer. In this way, the host cannot know in advance which command is set for the auxiliary bit set by the hard disk, and the DMA engine cannot be set before the data transfer cycle starts. This ultimately results in inefficient PATA hard drives.
NCQ contains two parts. On the one hand, the hard disk itself must be able to sort the read and write commands in the command buffer against the sector distribution of the physical data. Meanwhile, the commands in the internal queue of the hard disk can be dynamically readjusted or sorted with the necessary tracking mechanism. The tracking mechanism is used to grasp the status of pending and completed jobs, and the command queuing function can also enable the host to disconnect from the hard disk to release the bus when the device queues the command. Once the hard disk is ready, it is reconnected. To the host, transfer data as fast as possible to eliminate bus occupancy. On the other hand, the communication protocol support is also very important, because the previous PATA hard disk is very easy to cause interruption when transmitting data, which will reduce the efficiency of the master controller. Therefore, the interrupt aggregation mechanism defined in the NCQ specification is equivalent to one execution. After several commands, the finished information is sent back to the master controller to improve the performance of the processing queue command.
Starting from the earliest Seagate 7200.7 series hard drives, NCQ technology has been applied to desktop products for more than six months. However, NCQ does not bring much improvement in performance to personal desktop applications. In some cases, it may cause side effects. Moreover, there are differences in the NCQ schemes of different hard disk manufacturers and the effects are also different. Therefore, we must treat the NCQ wisely. Although there is one more technology that can improve the performance of the hard disk, it does not need to care.

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