What is the SATA data connector?
A SATA drive has two connectors side by side: a wide one for power and a narrow one for data. The SATA data connector is the narrow one, a 7-pin port with an L-shaped key. A thin SATA data cable runs from that port on the drive to a matching port on the motherboard or a controller card, and the L shape means it only goes in one way.
The seven pins are three grounds and two differential pairs, one for sending and one for receiving. SATA is point-to-point: each port connects one drive.
SATA data vs. SATA power
| SATA data | SATA power | |
|---|---|---|
| Pins | 7 | 15 |
| Size | Narrow | Wider |
| Comes from | A motherboard or controller port | A power supply cable or Molex-to-SATA adapter |
| Carries | Data signals | +3.3 V, +5 V and +12 V |
Speeds and revisions
All SATA revisions use the same data connector, and newer and older drives and ports work together at the slower side's speed.
| Revision | Line rate | Maximum throughput |
|---|---|---|
| SATA 1.0 (SATA I) | 1.5 Gb/s | About 150 MB/s |
| SATA 2.0 (SATA II) | 3 Gb/s | About 300 MB/s |
| SATA 3.0 (SATA III) | 6 Gb/s | About 600 MB/s |
Installation tips and quirks
- Port numbering: ports are labeled SATA0, SATA1 and so on (some boards start at 1). Ports on an extra controller chip may behave differently from the chipset's ports.
- Sharing with M.2: on many boards an M.2 slot shares lanes with one or more SATA ports, so installing an M.2 drive can disable them. If a SATA drive disappears after adding an M.2 SSD, check the manual.
- Cables: internal SATA cables can be up to 1 meter long. External drives use eSATA, which has its own shielded connector without the L key.
- SATA mode: the controller mode in BIOS/UEFI (AHCI or RAID) affects how the OS sees drives. Changing it after Windows is installed can stop Windows booting.
- Bad cables: CRC errors in S.M.A.R.T. data, dropouts or slow transfers often come from a damaged or loose data cable. Swapping the cable is a cheap first test.
For the CompTIA A+ exam
Core 1 (220-1201) objective 3.2 lists SATA and eSATA as hard drive cables, objective 3.4 includes SATA as an SSD interface, and objective 3.5 lists SATA among the motherboard connector types. Tell the 7-pin data connector from the 15-pin power connector by sight, and remember that a drive missing in the OS (an objective 5.2 symptom) can be as simple as an unplugged or failed data cable.