UK How a SATA connector works
A SATA connector is the connector that joins a storage drive to the computer’s Serial ATA controller. Serial ATA, defined by the Serial ATA International Organization (SATA-IO), replaced the wide 40-pin ribbon cables of parallel ATA in the early 2000s with a thin cable carrying data one bit at a time at much higher speed.
A standard 2.5-inch or 3.5-inch drive has two separate connectors side by side. The narrow 7-pin data connector carries two differential pairs, one to send and one to receive, separated by three ground pins. The wider 15-pin power connector brings three pins each of 3.3 V, 5 V and 12 V, plus grounds. Both are L-shaped, so a cable only fits one way.
The pins are staggered in length, so ground connects first and the signal last. With the controller in AHCI mode, that lets a drive be hot-plugged, which is how drive bays and removable storage trays work.
Types of SATA connector
SATA has grown several connector variants for smaller drives, embedded boards and external storage. The table shows the ones engineers still meet.
| Connector | Pins | Carries | Where you see it |
|---|---|---|---|
| Standard SATA data | 7 | SATA signal | Drives, motherboards, backplanes |
| SATA power | 15 | 3.3, 5 and 12 V | 2.5-inch and 3.5-inch drives |
| Slimline SATA | 7 data + 6 power | SATA signal, 5 V | Slim optical drives |
| Micro SATA | 7 data + 9 power | SATA signal, 3.3 and 5 V | 1.8-inch drives |
| eSATA | 7 | SATA signal, shielded | External drives and docks |
| eSATAp (Power over eSATA) | 11 or 13 | SATA, USB 2.0, 5 V and sometimes 12 V | Older laptops and combo ports |
Smaller storage formats drop the cable altogether. mSATA and M.2 SATA cards plug straight into the board, and a SATA DOM (disk on module) is a small flash drive that plugs directly into a SATA data port, taking power from a spare pin or a short lead. Our explainer on what a SATA SSD is and how fast it runs covers those drive formats in detail.
SATA revisions and speeds
Every SATA revision uses the same connectors and is backward compatible, so a newer drive works on an older port at the older speed. The usable speed is lower than the line rate because 8b/10b encoding uses 10 bits for every byte.
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SATA I (1.5 Gb/s). Around 150 MB/s. Found on equipment from the mid-2000s.
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SATA II (3 Gb/s). Around 300 MB/s. Still enough for most hard drives, which typically top out at around 250 to 280 MB/s.
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SATA III (6 Gb/s). Around 600 MB/s at the line, typically 550 MB/s in practice. The current speed for SATA SSDs.
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SATA Express (16 Gb/s). Defined in SATA 3.2 to run SATA or PCIe over a wider connector. Few products used it, and NVMe on M.2 took its place.
What eSATA is
eSATA (external SATA) took the SATA signal outside the case for external drives. It was standardised in 2004 and appeared on desktops, laptops and NAS boxes until USB 3.0 and Thunderbolt overtook it. Searches for eSATA ports today usually come from people identifying a port on older equipment.
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Different shape. The eSATA socket is straight-sided with no L key, so an internal SATA cable cannot be plugged in by mistake.
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Shielded and tougher. eSATA cables are shielded, can run up to 2 m against 1 m for internal SATA, and the connector is rated for far more mating cycles.
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No power on its own. Plain eSATA carries data only, so external drives need their own power supply. eSATAp combo ports added USB pins and 5 V to fix this.
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Same speed as internal SATA. eSATA runs at the speed of the controller behind it, up to 6 Gb/s, with no protocol translation, which once made it faster than USB 2.0.
SATA connectors in industrial systems
On a desk, SATA cables rarely cause trouble. On a vehicle, a machine or a rail system, a loose cable is a common cause of a drive vanishing from the system, so industrial builds treat the SATA connection as a reliability item.
The fixes are well known. Latching data cables lock into the drive and board. Short, routed and clamped cables stop the connector being levered out under vibration. Many of our rugged computers and fanless systems use M.2 or mSATA storage with no cable at all, keeping a 2.5-inch SATA bay only where a large or removable drive is needed. Boards such as our industrial Mini-ITX motherboards typically provide several SATA ports for drive arrays or RAID.
For drives that must survive power loss, industrial SATA SSDs add power-loss protection and wide-temperature NAND. Our guide to M.2 slots, keys and industrial SSDs explains when a cabled SATA drive still makes sense.
Quick answers on SATA connectors
SATA connectors: common questions
How many pins does a SATA connector have?
Seven for data and 15 for power. A standard drive has both connectors side by side, so 22 contacts in total. Slimline and micro SATA drives use smaller power connectors.
What does a SATA connector look like?
A flat, L-shaped plastic tab. The data connector is about a third the width of the power connector. Both have an L-shaped key so they only fit one way round.
Does eSATA provide power?
No, not plain eSATA. eSATA carries data only. eSATAp, or Power over eSATA, combines eSATA with USB and supplies 5 V, and sometimes 12 V, to power small external drives.
Is eSATA faster than USB 3.0?
Slightly, on paper. eSATA runs at up to 6 Gb/s with no protocol translation, against 5 Gb/s for USB 3.0, so a fast SSD can run a little quicker over eSATA. USB 3.1 Gen 2 and Thunderbolt are faster still and carry power, which is why they replaced it.
Are all SATA cables the same?
The connectors are, the quality is not. Any SATA data cable fits any SATA port, but cables differ in shielding and latching. For vibration, choose latching cables and keep them short.
We fit, route and secure the storage in every system we build as standard, choosing between SATA, mSATA and M.2 for the drive’s role, and clone the operating system image before the system ships. Tell us the capacity, endurance and temperature range you need, and we will specify the drive and connection to match.