BUS SATA (Serial Advanced Technology Attachment)


The computers are constituted by a series of technologies that act together. Processors, memories, chips graphics and other devices evolve and improve the experience user. With items such as hard disks, DVD players or Blu-ray , and SSD drives it could not be different. Interface SATA (Serial Advanced Technology Attachment) is the proof of that.

In this text you’ll learn more about this technology, as its differential in relation to the standard Paralell ATA (or IDE), the basic differences in their versions, as well as their main characteristics and their advantages.


The standard SATA (Serial ATA) is a technology for hard drives, optical drives, and other storage devices data that came on the market in the year 2000 to replace the traditional interface PATA (Paralell ATA, the only ATA or even IDE).

The name of both the technologies already indicates the main difference among them: the PAW makes the transfer of data in parallel, that is, transmits several bits at a time, as if they were side-by-side. In SATA, the transmission occurs in the series, such as if each bit were one behind the other.

Because of this, you can imagine that the PAW is faster, doesn’t it? In fact, it is not. The parallel transmission of data (generally with 16 bits at a time) causes a problem known as “noise”, that is nothing more than the loss of data caused by interference. To deal with the problem, manufacturers have implemented mechanisms in the HDs PATA to to decrease the noise. One of them is the recommendation use cables flat (the cable that connects the HD to the motherboard) with 80 lanes(that is, with eighty wires) instead of the traditional cables with 40-way. The way most act as a kind of shield against interference.

In the case of the SATA standard, the noise practically does not exist, same because your cable connection to the computer typically only has 4 lanes and it is also shielded. This ends up bringing another point of advantage to the SATA since, as the cable has a small size, the internal space the computer is best utilized, making it easier including the circulation air. The cable can also be larger, to be able to work without problems with 1 meter, for example.

In addition, the SATA technology works with frequencies (clock) higher in comparison to the PAW. Frequencies larger numbers result in more data transmitted per time, but open more room for noise (interference). However, the serial transfer serves as protection against this problem.

The standard Paralell ATA speed of the transmission limited data because of the noise. The last specification this technology is the ATA 133 that allows, at most, a transfer rate of 133 MB per second. The Serial ATA, for its instead, you can use speeds much larger.

There is another interesting feature in the SATA standard: Drives that use this interface do not need jumpers to identify the disk master (primary) or slave (secondary). This is because each device uses a single transmission channel (the PAW allows up to two devices per channel), hitching its total capacity to a single HD.

Not that there is no incompatibility with devices Paralell ATA, it is possible to install the HDs-type interfaces SATA by means of adapter plates. In addition, many manufacturers released models of the motherboards with both interfaces. This occurred mainly during the period of the transition from one technology to another. Today, it is quite difficult to find new devices with PATA interface.

Another interesting feature of SATA is the possibility of the use of the technical hot-swap, which makes it possible to exchange a device Serial ATA with the computer on. For example, it is can replace a HD without the need to shut down the machine for this. This feature is very useful in servers that need to maintenance/repairs, but can not stop working.

Worth stressing also that it is possible to find equipment type port multiplier that allow the connection of more than a device on a single SATA port, similar to what happens with the USB hubs.


Versions of the SATA interface

As with other technologies, the SATA standard it is perfected with the passing of time, a fact that results in new versions. The following is a brief description of the existing versions until the closing of this text.


The first version of the SATA works with maximum transfer rate data of 150 MB per second (MB/s). This version will also receive the following name: SATA 150, SATA 1.0, SATA 1,5 Gb/s (1.5 gigabits per second) or, as you already know, simply SATA I.

Theoretically, this version of SATA can work with rates transfer up to 1.5 Gb/s, resulting in a maximum range of 192 MB/s (megabytes per second). However, the interface uses an encoding scheme name 8B/10B which limits this speed at 1.2 Gb/s, something around 150 MB.

Encoding 8B/10B has this name because each set 8-bit is handled in a package of 10 bits. The two-bit additional are used for the purposes of synchronization, making the transmission of data more secure and less complex.

The frequency of the SATA I is 1.5 GHz.


Before long, there is a version called SATA II (SATA 3 Gb/s, SATA 2.0 or SATA 300) whose main characteristic is the speed of transmission data up to 300 MB/s, double that of SATA I, not being a little bit longer by also using encoding 8B/10B. This substantial gain speed is mainly due to the clock of this version, of 3 GHz.

Interestingly, many hard disks that use this specification can count with a jumper that limits the device speed up to 150 MB/s, a measure applied to do with these HDs to work on motherboards that only support the SATA I.

Here it is worth making a note: the entity that controls the SATA standard (formed by a group of manufacturers and related companies) it’s called today, SATA-IO (SATA International Organization). The problem is that the previous name this organization was SATA-II, which caused some confusion with the second version of the technology.

Taking advantage of this situation, many manufacturers have placed seals of the SATA-II on your HDs SATA 1.0 in an apparent attempt to confuse users less attentive, making them think that such disks were, in fact, the second generation of SATA hard Drives. This is why it is need to look carefully at the technical specifications the hard disk at the time of purchase.

Fortunately, a few models of hard Drives fit in this context. Any way, this situation highlights the fact that the names SATA I, SATA II and, later, SATA III, were never officially adopted, though its use in the market be common.


2009 was the year of release of the final set of specifications the third version of the technology, Serial ATA, called SATA III (SATA 6 Gb/s, SATA 3.0 or SATA 600). This standard allows, theoretically, transfer rates of up to 600 MB per second.

The SATA III also uses an improved version of the technology NCQ (discussed in the next topic), has better power management and is compatible with connectors for 1.8-inch specific for devices of small size. The default SATA III shows especially interesting for use in SSD drives, that through the use of memory of type Flash can achieve rates transfer higher than the hard disks.

Specification SATA III works with a frequency up to 6 GHz, also making use of encoding 8B/10B.

It is worth mentioning that, as for the aspect of speed, hardly the values mentioned above (150 MB,300 MB and 600 MB) are achieved. These rates indicate the maximum capacity transmission of data between the HD and the computer, but they are hardly used in its entirety, since it depends on a combination of factors, such as the content of the memory, processing, other technologies applied to the hard disk, etc.


Technologies related to the SATA

Manufacturers can add technology into their products to differentiate them in the market or to meet a particular demand, which means that certain features may not necessarily be mandatory on a hard disk just for this to be SATA. Let’s look at some of them:

– NCQ (Native Command Queuing): NCQ is taken as mandatory on SATA II, and SATA III, but was optional on the standard SATA I. this is a technology that allows the HD to organize the requests recording or reading data in an order that makes the heads move to the minimum possible, increasing (at least theoretically) the performance of the device and its useful life. To understand better the operation of NCQ here;

– Link Power Management: this feature allows HD to use less electrical energy. For this, the hard disk can take three states: active (active), partially active (partial) or inactive (slumber). Thus, the HD gets power according to your usage at the time;

– Staggered Spin-Up: this is a very useful feature systems RAID, for example, it allows you to enable or disable the HDs working together without interfering in the operation of the disk group. In addition, the technology Staggered Spin-Up also improves the distribution of energy between the disks;

– Hot Plug: in its essence, this feature allows you to connect the disk to the computer with a functioning operating system. This it is a very used resource in the HDs of the type removable.


Connectors and SATA cables

The connectors and cables used in SATA technology, offer two great advantages to the user: takes up less space inside the computer; and have fitting easier and more secure (it is virtually impossible to connect a SATA cable so, inverted). The same the valley to the power connector of the HD (or another compatible device). The following image shows a SATA cable conventional and its connectors:

Now look at the photo below. It shows a SATA connector on a HD. Note that there are also a larger connector, where it should be attached to the cable electrical power. This connector is more easy to be manipulated that the docking energy of the disks hard drives PATA:

The SATA connector is formed by seven routes:

  1. Ground (earth)
  2. The+ (data send)
  3. A- (send data)
  4. Ground (earth)
  5. B+ (receive data)
  6. B- (receive data)
  7. Ground (earth)

The channels A and B are for the data traffic itself. The channels with a negative symbol (A – and B-) are “replicas reversed” used as protection against interference: reception of data, signals + and – are compared and, from the differences, is possible to identify “noise” in the transmission. The the remaining pins are for grounding.

Note that, as there are pathways for sending and receiving data, the transmission in a SATA connection occurs in two senses, that is, it is a technology full-duplex, where is possible to receive and send information at the same time.


It is possible that you see the name mSATA (mini-SATA) somewhere. Not necessarily a new specification of the SATA, but a connection standard developed especially for SSD drives of small size that can be used, for example, on ultrabooks (laptops with a thickness small) or even tablets.

In this case, the drive SSD is usually provided in the format of a plate, having dimensions similar to that of a card credit. The idea here is to lessen the problem of fragmentation of formats and connectors, since each the manufacturer adopted a different standard.


From the term external SATA, eSATA it is a type of port that allows the connection of devices external a SATA interface of the computer. This feature is particularly interesting to users who wish to take advantage of the compatibility of external hard Drives with the SATA technology to achieve higher data transfer rates.

Many manufacturers offer motherboards and notebooks that rely on a port that works both as eSATA and USB, in addition, it is of course, a door that is only eSATA. For the cases where there is no this port, you can use the adapters that are installed slots PCI Express, for example.

The eSATA offers the advantage of allowing the use of the speed of the version of SATA in use, on the other hand, does not provide electrical power, which means that only devices with an external power source is it that they can use it.

One of the solutions found by the industry to to overcome this limitation is eSATAp, which is nothing more it is a scheme that uses a compatible USB port with eSATA in conjunction with two-pin power, typically 12 V. If it is necessary to use pins 5 V, you can use that is already provided by the USB port.


The Serial ATA standard began to be developed officially in the year 1997 and emerged from an initiative of Intel with the 70 companies, approximately. The idea was formed for the forecast what future technologies of data storage would require transfer rates until then not supported. The SATA technology proved to be as a solution to this issue without, however, have production costs higher as a result, one of the factors that have been determining factors for its wide acceptance in the market.

If you want to get more details about the technology, simply access the website the SATA International Organization.

Bus Sata (Serial Advanced Technology Attachment) 1

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