As technology evolves, the connectors and interfaces used for computer components change over time. This is especially true for hard drives, which have gone through several iterations of connectors as new standards emerged. Understanding the history and terminology for hard drive connectors can be helpful when trying to identify older hard drives or find compatible cables.
One of the earliest widespread hard drive interfaces was ATA, short for Advanced Technology Attachment. This interface was commonly used from the late 1980s through the 1990s for connecting hard drives to a computer’s motherboard. ATA connections use wide, flat cables with large connectors. There are a few variations of ATA connectors:
- PATA: Parallel ATA, the earliest version of the ATA interface. PATA cables have 40 or 80 pins and transmit data in parallel.
- EIDE: Enhanced IDE, an improved version of PATA supporting larger capacity hard drives. EIDE connectors look nearly identical to PATA.
- ATA-2/ATA-3: Later versions of parallel ATA that increased performance. Used the same type of connector as PATA/EIDE.
PATA, EIDE, and ATA connectors all use the same flat 40 or 80 pin interface cables to connect hard drives to a motherboard controller. They transfer data in parallel, with multiple data bits sent simultaneously over cable wires. The large flat connectors became colloquially known as “IDE cables” during the 1990s as EIDE standard drives increased in popularity. The terms PATA, EIDE, and 40/80-pin IDE all refer to the same kind of flat, wide multi-pin parallel ATA drive connectors still found on older hard drives today.
In the early 2000s, the SATA (Serial ATA) standard replaced parallel ATA interfaces for hard drive connections. SATA connectors are much smaller and transmit data serially instead of in parallel. Some common SATA connector types include:
- SATA 1.5Gb/s: The original SATA specification, providing 1.5 Gb/s speeds.
- SATA 3Gb/s: Later SATA version supporting 3 Gb/s transfer rates.
- SATA 6Gb/s: SATA revision supporting 6 Gb/s speeds.
The SATA interface uses skinny 7-pin cables instead of the bulky 40/80-pin cables used for PATA/EIDE. SATA connectors are about 1/3 the size of PATA connectors and have an “L” shaped design. The smaller size allows SATA cables to be more flexible with tighter bend radiuses. They also latch and lock in place for a more secure connection.
eSATA is an extension of the SATA interface designed for external connections. eSATA ports and cables are designed for plugging external hard drives and enclosures directly into a computer. eSATA connectors look very similar to internal SATA connectors, but the interface uses more durable cables with higher tolerances for external connections.
SAS, or Serial Attached SCSI, is another serial interface used primarily for connecting enterprise-level hard drives and solid state drives. SAS connectors resemble SATA but are physically incompatible. SAS uses a thicker “I” shaped connector with more pins and supports multiple connections via one cable.
Before SATA and SAS, SCSI (Small Computer System Interface) was widely used for hard drives, especially on servers and workstations. The SCSI interface uses ribbon cables with large edge connectors, similar to PATA. There are several types of SCSI connector:
- HSCSI: High-bandwidth SCSI, capable of up to 80 MB/s transfer rates.
- SCSI-1: The original SCSI specification, launched in 1986.
- Wide SCSI: Variant of SCSI that uses wider cables for improved performance.
- SCSI-2: Released in the 1990s, SCSI-2 doubled performance over SCSI-1.
- Ultra SCSI: Introduced in Fast/Wide SCSI, Ultra SCSI boosted speeds up to 40 MB/s.
- SCSI-3: The 1996 SCSI-3 standard increased speed to 80 MB/s and supported wide connectors.
The SCSI interface went through many iterations, but all SCSI connectors use the same parallel bus technology. Cables have wide ribbon connectors with exposed pins that slot into edge connectors on hard drives. Number of pins range from 50-pin SCSI to 68-pin SCSI and 80-pin SCSI, with the wider interfaces supporting faster speeds.
FC and Fibre Channel
Fibre channel is a very high speed interface primarily used in storage area networks (SAN). It allows for transmission over long distances using fiber optic cables. There are several types of fibre channel connectors:
- Narrow FC: Uses 8-bit transmission width.
- Wide FC: 16-bits wide for added throughput.
- FC-AL: Supports arbitrated loops with hubs/switches.
- FC-PLDA: Supports point-to-point cabling.
Common fiber channel connector types include LC, MT-RJ, SC, ST, and MPO. FC connectors are rectangular and lock in place with a latching mechanism when inserted. Fibre channel interfaces achieve speeds up to 128 Gb/s for very high performance storage networks.
USB and FireWire Connectors
USB and FireWire interfaces are common for external hard drive enclosures. These interfaces use simple serial bus structures:
- USB: Universal Serial Bus, ubiquitous on computers today. USB connectors are rectangular with 4 pins/contacts.
- USB 1.0/1.1: Original USB specs supporting up to 12 Mb/s speeds.
- USB 2.0: Supports up to 480 Mb/s transfer rates.
- USB 3.0/3.1: Newest USB standard supporting 5 Gb/s.
- USB-C: Reversible oval shaped USB connector for latest devices.
- FireWire 400: Supports 393 Mb/s transfer rates.
- FireWire 800: Doubles throughput to 786 Mb/s.
Most external portable hard drives today use either USB or FireWire interfaces. USB handles communication while FireWire additionally provides power over the bus. Both use simple cables with small connectors, making them convenient for attaching external hard drive enclosures.
A more recent external interface used on hard drives and enclosures is Thunderbolt. Introduced in 2011, Thunderbolt combines PCI Express and DisplayPort protocols over one serial connection. Thunderbolt connectors are small and have the same reversible USB-C style design. Thunderbolt cables carry 20 Gb/s bandwidth for high performance external storage connections.
M.2 connectors are a new form factor designed for small, high speed solid state drives (SSDs). M.2 connectors slot directly into a motherboard or adapter card. While technically not a drive connector, M.2 SSDs are replacing traditional hard drives in many computers. M.2 uses multiple lanes of PCI Express bus and supports transfer speeds up to 32 Gb/s depending on the implementation.
CFexpress and CFast
CFexpress and CFast are connectors used on some solid state drives designed for professional media creation. They represent another new form factor beyond traditional SATA or M.2 SSDs. Both use PCI Express and NVMe interfaces to achieve very high read/write speeds with low latency. CFexpress uses the same form factor as SD cards while CFast looks like a compact CompactFlash card.
The mSATA interface is designed for solid state drives to be used in laptops, tablets, and other portable devices. The compact mSATA connector is a variation of SATA designed for small form factor SSDs. mSATA drives are about 1/8th the size of a standard 2.5 inch SATA SSD and connect directly to an internal PCI Express-to-mSATA adapter slot.
ZIF stands for zero insertion force. ZIF connectors are used for certain types of solid state drives like Apple’s 1.8 inch microdrive SSDs. ZIF connectors allow drives to be inserted and removed without any force, instead using a movable locking arm to secure the connection. ZIF connectors help protect very delicate SSD pins and connectors from damage during insertion/removal.
U.2 connectors, formerly known as SFF-8639, are designed for connecting high performance NVMe SSDs. They provide a way to use new NVMe drives while maintaining compatibility with existing systems. U.2 connectors utilize PCI Express technology while using the same 2.5 inch drive form factor as standard SATA drives. U.2 allows NVMe performance benefits without major system changes.
Hard drive interfaces have evolved from bulky parallel cables to much smaller and faster serial connections. Older hard drives typically used wide PATA/IDE connectors or SCSI ribbon cables that plugged into edge connectors. Newer SATA connectors are much smaller and easier to work with. External hard drives now use interfaces like USB, Thunderbolt, or FireWire. For the fastest speeds with solid state drives, new form factors like M.2 and U.2 connectors plug drives right into PCI Express slots. While technology continues to improve, understanding legacy hard drive connectors helps identify and properly connect older drives.