Hard drives store digital information on rotating magnetic disks inside a protective case. They connect to a computer’s motherboard using an interface, which is the hardware and software protocol that enables communication between the hard drive and computer.
Hard drive interfaces have evolved over the years to enable faster transfer speeds and handle larger amounts of data. Some common interfaces used over the past few decades include Integrated Drive Electronics (IDE), Small Computer System Interface (SCSI), Serial ATA (SATA), and USB.
As technology has advanced, the amount of data that can be stored on hard drives has grown exponentially. For example, in 1956 one of the first hard drives could store just 5MB, whereas modern hard drives can store 10TB or more. To handle these massive capacities, interface technology has had to improve drastically.
History of Hard Drive Interfaces
The first commercial hard disk drive was the IBM 350 disk storage unit released in 1956. It was the size of two refrigerators and stored 5 million characters (around 4.4MB) on fifty 24-inch disks (Wikipedia, 2022). In the 1960s and 1970s, hard drives continued to rapidly grow in storage capacity while shrinking in physical size.
Some key developments in hard drive interfaces during this period were:
- Integrated Drive Electronics (IDE): Introduced in the mid-1980s, IDE integrated the disk controller directly on the hard drive itself, eliminating the need for a separate controller card. IDE provided an interface standard that allowed different manufacturers to create compatible drives and controllers (Wikipedia, 2022).
- Small Computer System Interface (SCSI): Introduced in the early 1980s, SCSI emerged as a standard parallel interface that allowed linking of devices externally to a computer. It offered improved performance over IDE and supported more devices on a single controller (Wikipedia, 2022).
- Serial ATA (SATA): Released in 2001, SATA replaced the parallel ATA physical storage interface with a serial one, providing higher speeds and hot swapping capabilities. SATA became the most common hard drive interface for desktop and laptop PCs in the 2000s (Backblaze, 2016).
These interfaces enabled hard drives to gain vastly improved performance and storage capacities from their roots as refrigerator-sized units storing just a few megabytes.
Integrated Drive Electronics (IDE)
IDE, also known as ATA, was introduced in the late 1980s as an interface standard for connecting hard drives to personal computers. IDE stood for Integrated Drive Electronics and integrated the hard drive controller directly onto the drive itself, eliminating the need for a separate controller card.
IDE provided a 40-pin connector that made attaching hard drives to computers much easier compared to earlier interface standards like ST-506. The widespread adoption of IDE in the 1990s was a key factor in making hard drives commonplace in desktop PCs. IDE allowed for easier installation and configuration and helped drive down the cost of storage as IDE drives could be directly connected without requiring a dedicated drive controller.
The initial version of IDE supported up to two hard drives and transfer speeds up to 16.6 MB/s. Later versions like Enhanced IDE (EIDE) and Ultra DMA increased the maximum throughput to 133 MB/s. IDE became the dominant hard drive interface for consumer PCs throughout the 1990s and much of the 2000s until being gradually replaced by Serial ATA.
Sources:
https://www.techtarget.com/searchstorage/definition/IDE
Small Computer System Interface (SCSI)
The Small Computer System Interface (SCSI) is a set of interface standards for physically connecting and transferring data between computers and peripheral devices like hard drives, solid-state drives, tape drives, CD/DVD drives, printers, and scanners. SCSI interfaces were commonly used from the mid-1980s into the 2000s.
SCSI stands for Small Computer System Interface. It was originally developed in the early 1980s as a standard interface protocol to allow personal computers to connect with peripheral devices like hard drives and printers (Wikipedia, 2022). The key benefit of SCSI interfaces was the ability to daisy chain multiple devices together on a single controller port, avoiding the need for separate cards or ports for each device.
SCSI uses a client-server architecture, where the devices connected are either SCSI initiators or SCSI targets. The initiator device issues commands, while the target devices listen for commands and carry them out. For example, the computer would be the initiator sending commands to SCSI hard drives or printers to request data transfers or perform operations (TechTarget, 2022).
Some key characteristics of SCSI interfaces are:
- High data transfer speeds for the time
- Ability to connect multiple devices on a single controller
- Standardized communication protocols
- Hot swappable devices
SCSI interfaces were widely used for connecting hard drives, tape drives, CD/DVD drives, printers, scanners and other devices from the mid-1980s into the 2000s. However, faster serial interfaces like USB and SATA have mostly replaced parallel SCSI interfaces today.
Serial ATA (SATA)
Serial ATA (SATA) emerged in the early 2000s as a replacement for the Parallel ATA (PATA) interface. SATA was designed to improve speed and simplify cabling compared to PATA. The first SATA specification, known as SATA 1.0, was released in 2001 and offered a maximum bandwidth of 150MB/s. This was a significant increase over the 133MB/s maximum of PATA. SATA also uses much thinner cables, making it easier to connect drives and improving airflow in computers. By 2003, SATA began to replace PATA in desktop computers and commodity server systems.
According to the TechTarget article on SATA, “SATA is a serial version of the Integrated Drive Electronics (IDE) specification for PATA hard drives that use parallel signaling” (Source). The emergence of SATA marked a major evolution in hard drive interfaces, enabling faster speeds in a simpler form factor. SATA has continued to evolve over the years, with newer versions increasing maximum bandwidth to 600MB/s and beyond.
USB
USB (Universal Serial Bus) has become a common interface for connecting external hard drives. USB offers plug-and-play functionality that allows easy connection of external drives without needing to install drivers or reboot the system. Most computers today come with multiple USB ports, making it convenient to use USB hard drives.
External USB hard drives typically connect to a computer via a USB cable. Common USB versions used for external storage include USB 3.0, USB 3.1 Gen 1 (5 Gbps), and USB 3.2 Gen 2 (10 Gbps), which offer faster data transfer speeds compared to older USB 2.0. Many external hard drives today use USB Type-C connectors. USB’s ease of use, speed, and ubiquity make it one of the most popular interfaces for external storage.
According to research by PCMag, many of the top external hard drives today like the Western Digital My Passport, Seagate Backup Plus Slim, and Samsung T5 rely on USB connectivity with housings that are light and easily portable. While interfaces like Thunderbolt offer faster speeds, USB remains the most common thanks to its nearly universal support across laptops, desktops, tablets, and more. USB’s speed, simplicity, and prevalence make it the interface of choice for most external hard drives for general consumer use.
Thunderbolt
Thunderbolt is a hardware interface developed by Intel and Apple in 2011 that allows for fast data transfer speeds between peripheral devices and computers. Thunderbolt combines PCI Express (PCIe) and DisplayPort into one serial signal, providing high bandwidth of up to 40 Gb/s bi-directionally (80 Gb/s total). This allows users to connect external devices such as hard drives, docking stations, display screens, and RAID arrays using a single port.
For external hard drives, Thunderbolt offers extremely fast read/write speeds compared to USB or FireWire. A Thunderbolt hard drive can provide up to 1000-1500 MB/s sequential read/write performance. This speed makes it ideal for activities like video editing, gaming, or transferring large files. The interface supports daisy-chaining up to 6 Thunderbolt devices, meaning you can connect multiple drives and accessories using a single Thunderbolt port on your computer.
Some of the fastest external Thunderbolt hard drives available today include models like the LaCie 2big RAID (https://www.bestbuy.com/site/lacie-2big-raid-16tb-external-usb-3-1-gen-1-hard-drive-black/6426862.p?skuId=6426862) which provides up to 440 MB/s speeds, and the Samsung X5 Portable SSD (https://www.amazon.com/Samsung-Portable-SSD-Thunderbolt-MU-PB500B/dp/B07GBW1WXW) with read speeds up to 2800 MB/s.
Most Common Interface Today
The most prevalent hard drive interface in desktop and laptop computers today is SATA (Serial ATA). SATA was designed to replace the older PATA (Parallel ATA) standard and has become the default hard drive interface for the majority of consumer devices over the last 15+ years.[1] SATA3, the latest version of the SATA interface, provides transfer speeds up to 6 Gbit/s and is backwards compatible with previous SATA versions.[2]
Compared to earlier hard drive interfaces like PATA/IDE and SCSI, SATA offers faster data transfer rates, a simpler cable design with less bulk, native hot swapping support, and lower power requirements. These advantages have made SATA the go-to interface for connecting not just hard disk drives, but also solid state drives, optical drives, and other storage devices to motherboards and controllers in modern desktop and laptop PCs.[3]
While other interfaces like USB and Thunderbolt are used for external storage devices, internal storage in today’s computers overwhelmingly utilizes the SATA interface. For system builders and PC users, SATA’s dominance means storage devices like hard drives and SSDs are universally compatible with modern motherboards and controllers that incorporate SATA ports.
Trends and Future Interfaces
There are several emerging interfaces that are likely to become more common in the future. Some of the key trends include:
- PCIe (Peripheral Component Interconnect Express): PCIe is a high-speed serial interface that is already common in SSDs. PCIe 4.0 offers transfer speeds up to 16GB/s, with PCIe 5.0 reaching 32GB/s. Using the NVMe protocol over PCIe allows for extremely fast data transfer speeds compared to older interfaces like SATA.
- NVMe (Non-Volatile Memory Express): NVMe is a protocol designed for PCIe interfaces to unleash the speed potential of SSDs. NVMe offers higher queue depths, lower latency, and parallelism compared to AHCI used with SATA. NVMe over PCIe allows SSDs and future storage drives to operate at maximum throughput.
- USB4: USB4 is the newest USB standard, supporting 40Gbps transfer speeds when using two lanes. This is double the bandwidth of USB 3.2. USB4 builds off Thunderbolt 3 but offers wider compatibility. External SSDs are already taking advantage of USB4’s high speed potential.
These emerging interfaces point to a future with incredibly fast external storage options. As bandwidth increases, there will be less need for the moving parts of traditional hard drives. SSDs and future technologies like ReRAM and MRAM will be able to fully utilize the bandwidth potentials of PCIe, NVMe, and USB4.
Conclusion
In summary, the most common interface used today to connect hard drives in desktop PCs and laptops is Serial ATA (SATA). SATA has been widely adopted over the past 15+ years, replacing Parallel ATA/IDE and SCSI as the interface of choice for consumer storage.
SATA provides significant advantages over earlier interfaces, including faster data transfer speeds, smaller cable size, and hot swappability. The SATA interface has gone through several revisions, with SATA 3.0 (6Gbps) being the most current version used for connecting solid state drives and hard disk drives.
While newer interfaces like Thunderbolt and USB have emerged, SATA remains the dominant hard drive interface, especially for internal storage in desktops and laptops. As drive and interface technologies continue to evolve, SATA is likely to remain relevant for the foreseeable future.