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SATA Cables Explained
SATA data cables are used to connect storage devices to your computer's motherboard ("mobo") or SATA controller.
What is a SATA Cable?
SATA (also referred to as Serial ATA) stands for Serial Advanced Technology Attachment, an industry-standard bus interface for connecting a computer's host bus adapter to storage devices such as hard disk drives (HDD), optical drives and solid-state drives (SSD).
SATA cables are typically used inside a computer's case. eSATA cables connect external devices outside of the computer case and support data transfer but not power (the assumption being that external devices have their own power supply). eSATAp (Power over eSATA) is a combination of eSATA and USB. An eSATAp port accepts an eSATA or USB connector and provides both data transfer and power.
Standard, wafer-style SATA connectors come in male and female formats and are available in three varieties: data only, power only and data plus power. Wafer-style connectors have pins arranged in a single row, making them wider but capable of mating with small devices like SSDs.
SATA Data Connectors
A SATA data connector has 7 horizontal pins, four pins arranged in two pairs for data and 3 ground pins. One end (the end that connects to a storage device) may be angled to save space.
A small form factor version of the SATA data connector, known as mini-SATA or mSATA connector is designed for use with smaller, power-constrained devices such as laptops and tablets.
SATA Power Connectors
The SATA power connector has 15 pins and supplies +3.3V DC, +5V DC and +12V DC. SATA power cables are often paired with a 4-pin Molex LP4 connector, which connects to a computer's power supply.
Less common SATA power connectors are the 6-pin, +5 VDC "Slimline" connector first introduced in SATA release 2.6, and the 9-pin, +3.3 VDC and +5 VDC micro connector for 1.8-inch (46 mm) hard disk drives.
A twinaxial ("twinax") SATA data cable is typically flat with its 4 copper conductors arranged side-by-side in pairs with a gap in between. SATA uses differential signaling to reduce electromagnetic interference (EMI) or crosstalk (interference from the other conductors in the cable). Differential signaling also requires a lower voltage, which reduces power consumption.
SATA cables can be up to a meter (3.3 feet) in length but attenuation (signal loss) can be minimized by using the shortest possible cable for internal and external connections. eSATA cables can be up to 2 meters (6.6 feet) in length and support multiple devices on a single port/cable.
Data Transfer Speeds
Since its introduction in 2003, the SATA interface has undergone three major revisions. The primary difference between versions is data transfer speed.
|Standard||Bandwidth*||Data Transfer Speed|
|SATA I||1.5 Gb/sec||150 MB/sec|
|SATA II||3 Gb/sec||300 MB/sec|
|SATA III||6 Gb/sec||600 MB/sec|
SATA III cables (also referred to as SATA 3 cables) are backward compatible with earlier standards so SATA II rated devices will function but at a reduced speed. For example, a solid-state drive connected to SATA III (6 Gbps) port can read at speeds up to 550 Mbps. When the same drive is connected to SATA II (3 Gbps) port, read operations will be limited to 285 Mbps.
SATA Cable Features
The ability to plug or unplug a device without powering down the computer is known as hot-swapping. SATA connectors and devices employ a two-step mating process to avoid arcing and power drops that might affect other loads. The 4 and 12 ground pins on a SATA power connector are longer so they make contact first when mated. Similarly, SATA devices have longer 3, 7 and 13 power pins for the same reason. Hot-swapping is a feature of the SATA controller.
To ensure a solid connection and to avoid accidental disconnections, SATA cables will typical feature latching connectors.
Space inside a computer case is often tight so angled connectors are an important consideration when choosing a cable. When installing a HDD or SSD horizontally, a left-angled connector feeds the cable up and along the top of the drive. A right-angled connector feeds the cable down. The angle of the connector is also important when drives are installed vertically and side-by-side.
My computer does not have an eSATA port on the back of the case. How can I connect my external hard drive?
PCs do not normally come with an eSATA port but you can easily add one for about $7 USD using Eaton Model Number P952-002. You would then connect your external device to the eSATA port using a eSATA cable (Model Number P950-02M).
Why does a SATA power connector have so many pins?
The 15-pin SATA power connector replaced the 4-pin Molex connector. Why the much greater pin count?
- Support for three voltages (3.3V, 5V and 12V).
- Avoids confusion with the 7-pin SATA data connector.
- Additional ground pins to support device hot-swapping.
- Advanced features such as delayed spin-up for mechanical drives.
What does M.2 SATA mean?
The M.2 connector interface (also known as NGFF) is designed for internally mounted expansion cards such as a Solid State Drive (SDD). It supports the SATA III, USB 3.0 and PCIe (NVMe) bus interfaces. M.2 can also be used by external enclosures like the U457-1M2-SATAG2 to connect SSDs.
Related SATA Products
SATA to eSATA Transitions Cable
These 7-pin to 7-pin transition cables, like the P952-18i, connect external devices with an eSATA port to an internal SATA controller. You can also add an eSATA port to your desktop PC using P952-002.
SATA to USB Adapter Cables
Most modern laptops and PCs have USB ports for external devices. These adapter cables let you connect a SATA HDD or SDD to a USB-A or USB-C port and are ideal for recovering data from an old PC or drive.
HDD and SSD Enclosures
These enclosures let you easily add storage to a laptop or PC using a USB-A, USB-B, USB-C or Thunderbolt 3 port.
SATA Hard Drive RAID Enclosures
RAID creates a virtual disk from multiple physical disk. It is used to improve performance by concurrently reading or writing to multiple disks or to provide data redundancy by writing data to two or more drives. RAID enclosures for SATA drives like the U457-2M2-SATAG2, configured for RAID Level 0, read data up to 70% faster and write up to 40% faster than a single drive.
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