Computers are made up of a series of technologies that work together. Processors, memories, graphics chips and other devices evolve and improve the user experience. With items like hard drives, DVD or Blu-ray players and SSD drives it could be no different. The SATA interface is proof of this. According to AbbreviationFinder.org, SATA stands for Serial Advanced Technology Attachment.
In this text, you will learn more about this technology, such as its differentials in relation to the Paralell ATA (or IDE) standard, the basic differences of its versions, as well as its main characteristics and advantages.
SATA x IDE (PATA)
The SATA standard (Serial ATA) is a technology for hard drives, optical drives and other data storage devices that appeared on the market in 2000 to replace the traditional PATA interface (Paralell ATA, only ATA or, even, IDE).
The name of both technologies already indicates the main difference between them: PATA transfers data in parallel, that is, it transmits several bits at a time, as if they were side by side. In SATA, the transmission occurs in series, as if each bit were one behind the other.
Because of that, you can imagine that PATA is faster, right? In fact, it is not. Parallel data transmission (usually 16 bits at a time) causes a problem known as “noise”, which is nothing more than the loss of data caused by interference. To deal with the problem, manufacturers have implemented mechanisms on PATA hard drives to reduce noise. One of them is the recommendation to use flat cables (the cable that connects the HD to the motherboard) with 80 ways (that is, with eighty wires) instead of the traditional cables with 40 ways. The extra routes act as a kind of shield against interference.
In the case of the SATA standard, the noise practically does not exist, not least because its connection cable to the computer usually has only 4 ways and is also shielded. This ends up bringing another advantage to SATA, because as the cable has reduced dimensions, the internal space of the computer is better used, even facilitating the air circulation. The cable can also be bigger, being able to work without problems having 1 meter, for example.
In addition, SATA technology works with higher clock frequencies compared to PATA. Higher frequencies result in more data being transmitted at a time, but make more room for noise (interference). However, serial transfer serves to protect against this problem.
The Paralell ATA standard has its data transmission speed limited due to noise. The latest specification of this technology is ATA 133, which allows a maximum transfer rate of 133 MB per second. Serial ATA, in turn, can use much higher speeds.
There is another interesting feature in the SATA standard: HDs that use this interface do not need jumpers to identify the master (primary) or slave (secondary) disk. This is because each device uses a single transmission channel (PATA allows up to two devices per channel), linking its total capacity to a single HD.
To avoid incompatibility with Paralell ATA devices, it is possible to install hard drives of the type on SATA interfaces through adapter cards. In addition, many manufacturers have launched motherboard models with both interfaces. This occurred mainly during the transition period from one technology to another. Today, it is quite difficult to find new devices with a PATA interface.
Another interesting feature of SATA is the possibility of using the hot-swap technique, which makes it possible to exchange a Serial ATA device with the computer on. For example, it is possible to change an HD without having to turn the machine off for that. This feature is very useful on servers that need maintenance/repairs, but cannot stop working.
It is also worth mentioning that it is possible to find equipment such as port multiplier that allows the connection of more than one device on a single SATA port, similar to what happens with USB hubs.
Versions of the SATA interface
As with other technologies, the SATA standard is improved over time, which results in new versions. The following is a brief description of the existing versions until the closing of this text.
SATA I
The first version of SATA works with a maximum data transfer rate of 150 MB per second (MB/s). This version also receives the following names: SATA 150, SATA 1.0, SATA 1.5 Gb/s (1.5 gigabits per second) or, as you know, just SATA I.
Theoretically, this version of SATA can work with transfer rates of up to 1.5 Gb/s, resulting in a maximum range of 192 MB/s (megabytes per second). However, the interface uses an 8B/10B name encoding scheme that limits this speed to 1.2 Gb/s, somewhere around 150 MB.
The 8B/10B encoding has this name because each set of 8 bits is handled in a 10-bit packet. The two additional bits are used for synchronization purposes, making data transmission more secure and less complex.
The frequency of SATA I is 1.5 GHz.
SATA II
It didn’t take long for a version called SATA II (SATA 3 Gb/s, SATA 2.0 or SATA 300) to emerge whose main characteristic is the data transmission speed of up to 300 MB/s, twice as much as SATA I, not being a little greater because it also uses 8B/10B encoding. This substantial speed gain is mainly due to the 3 GHz version’s clock.
Interestingly, many hard drives that use this specification can have a jumper that limits the device’s speed to 150 MB/s, a measure applied to make these hard drives work on motherboards that support only 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) is currently called SATA-IO (SATA International Organization). The problem is that the previous name of this organization was SATA-II, which created some confusion with the second version of the technology.
Taking advantage of this situation, many manufacturers have inserted SATA-II stamps on their SATA 1.0 hard drives in an apparent attempt to confuse the less attentive users, making them think that these drives were, in fact, of the second generation of SATA hard drives. So it is necessary to look carefully at the technical specifications of the hard drive at the time of purchase.
Fortunately, few HD models fit in this context. Anyway, this situation highlights the fact that the names SATA I, SATA II and, later, SATA III, were never officially adopted, despite their common use in the market.
SATA III
2009 was the year of launch of the final set of specifications for the third version of Serial ATA technology, called SATA III (SATA 6 Gb/s, SATA 3.0 or SATA 600). This standard theoretically allows transfer rates of up to 600 MB per second.
SATA III also uses an improved version of NCQ technology (covered in the next topic), has better power management and is compatible with 1.8-inch connectors specific to small devices. The SATA III standard is especially interesting for use in SSD drives, which, because they use Flash-type memory, can achieve higher transfer rates than hard drives.
The SATA III specification works with a frequency of up to 6 GHz, also making use of the 8B/10B encoding.
It is worth noting that, in terms of speed, it is difficult to reach the mentioned values (150 MB, 300 MB and 600 MB). These rates indicate the maximum data transmission capacity between the HD and the computer, but they are hardly used in their entirety, since this depends on a combination of factors, such as memory content, processing, other technologies applied to the hard disk, etc.
Technologies related to SATA
Manufacturers can add technologies to their products to differentiate them in the market or to meet a specific demand, which means that certain features may not necessarily be mandatory on a hard drive just because it is SATA. Let’s look at some of them:
– NCQ (Native Command Queuing): NCQ is considered mandatory in SATA II and SATA III, but it was optional in the SATA I standard. It is a technology that allows HD to organize requests for recording or reading data in an order that makes the heads move as little as possible, increasing (at least theoretically) the performance of the device and its useful life. Better understand the operation of the NCQ here ;
– Link Power Management: this feature allows the HD to use less electricity. For this, the hard disk can assume three states: active (active), partially active (partial) or inactive (slumber). Thus, the HD receives energy according to its use at the moment;
– Staggered Spin-Up: this is a very useful feature in RAID systems, for example, as it allows you to enable or disable hard drives working together without interfering with the operation of the disk group. In addition, Staggered Spin-Up technology also improves the distribution of energy between discs;
– Hot Plug: in essence, this functionality allows you to connect the disk to the computer with the operating system in operation. This is a feature widely used on removable hard drives.
SATA connectors and cables
The connectors and cables used in SATA technology offer two major advantages to the user: they take up less space inside the computer; and have an easier and more secure fit (it is practically impossible to connect a SATA cable in reverse). The same goes for the HD power connector (or other compatible device).
Now look at the photo below. It shows a SATA connector on a hard drive. Note that there is also a larger connector, where the power supply cable must be fitted.
The SATA connector consists of seven ways:
- Ground
- A + (sending data)
- A- (sending data)
- Ground
- B + (data reception)
- B- (data reception)
- Ground
Channels A and B serve the data traffic itself. The channels with a negative symbol (A- and B-) are “inverted replicas” used as protection against interference: when receiving data, the + and – signs are compared and, based on the differences, it is possible to identify “noise” in the streaming. The other pins are for grounding.
Realize that, as there are ways to send and receive data, transmission over a SATA connection occurs in both directions, that is, it is a full-duplex technology, where it is possible to receive and send information at the same time.
mSATA
You may see the name mSATA (mini-SATA) somewhere. This is not necessarily a new SATA specification, but a connection standard developed especially for small SSD units that can be used, for example, in ultrabooks (notebooks with small thickness) or even tablets.
In this case, the SSD unit is usually supplied in the form of a card, having dimensions similar to that of a credit card. The idea here is to alleviate the problem of fragmentation of connector formats, since each manufacturer adopted a different standard.
eSATA
Coming from the term external SATA, eSATA is a type of port that allows the connection of external devices to a computer’s SATA interface. This feature is particularly interesting for users who want to take advantage of the compatibility of external hard drives with SATA technology to achieve higher data transfer rates.
Many manufacturers offer motherboards and notebooks that have a port that works both as an eSATA and as a USB, plus, of course, a port that is just eSATA. For cases where this port is not available, adapters that are installed in PCI Express slots, for example, can be used.
ESATA offers the advantage of allowing you to take advantage of the speed of the version of SATA in use, on the other hand, it does not provide electrical power, which means that only devices with an external power source are able to use it.
One of the solutions found by the industry to overcome this limitation is eSATAp, which is nothing more than a scheme that uses a USB port compatible with eSATA in conjunction with two power pins, usually 12 V. If pins are required 5 V, you can use what is already provided by the USB port.
Conclusion
The Serial ATA standard began to be officially developed in 1997 and emerged from an initiative by Intel with approximately 70 companies. The idea was formed by predicting that future data storage technologies would require transfer rates that were not previously supported. SATA technology proved to be a solution to this issue without, however, having higher production costs as a consequence, one of the factors that were decisive for its wide acceptance in the market.
