Solid state drive (SSD) technology for the masses turned 30 this year. When it first launched, there was great anticipation, and for good reason. From the start, SSDs were faster and more reliable than traditional hard disk drives (HDDs). As the technology evolved, the chasm between HDDs and SSDs widened. Today, you’d be hard-pressed to find any computing device sold without an SSD installed or SSD compatibility.

The implementation of SSDs became even more pronounced in 2003 with the development of a low-latency computer expansion bus known as a peripheral component interconnect express (PCIe). A PCIe is a bus featuring high data transfer rates and little to no slow down.

So what is PCIe SSD used for, exactly? And why should you care? Below, we address four top questions about this technology and why it’s something that both consumers and businesses need.

1. What is PCIe SSD?

PCIe SSDs are like other SSDs in that they use flash memory to store files and applications. Flash, unlike traditional HDDs, has no moving parts. It uses solid state chips that feature flash memory cells to retain data regardless of whether the system is turned on or not, and software is used to retrieve that data when it’s needed. HDDs, in contrast, have an actuator arm that physically reaches out and writes and reads data on a spinning disk. PCIe SSDs are distinct from other SSDs in that they access the computer’s PCIe slot, which is also used for high-speed video cards, memory and chips.

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In 2003, PCIe 1.0 originally launched with a transfer rate of 2.5 gigatransfer per second (GT/s) and a total bandwidth of 8Gbps. (GT/s relates to the number of bits per second that the bus can move or transfer.) PCIe 2.0 doubled both the bandwidth and the gigatransfer, hitting 16Gbps and 5 GT/s, and the next generations doubled with each new iteration. PCIe 3.0 features 32Gbps bandwidth and 8 GT/s. PCIe 4.0 has 64Gbps bandwidth and a 16 GT/s rate. That said, the cards are limited by the slots they go into, so if you put a PCIe 4.0 SSD card into a 2.0 slot, the performance can only achieve 2.0 rates.

2. What’s the difference between a SATA-based SSD and a PCIe-based SSD?

PCIe SSDs are the most recent option available. There are actually four types of SSD form factors: serial advanced technology attachment (SATA), small computer system interface (SCSI), Fibre Channel, which was originally created for network-attached devices, and PCIe.

In the past, most SSDs connected to a computer via a SATA slot. SATA was built with HDDs in mind, and uses a special cable to connect a drive to the motherboard. This slot allows the SSD to read data at speeds of up to 550MBps and write at around 500MBps. As mentioned, PCIe SSDs connect directly to the PCIe slot. A PCIe SSD is smaller in size than a SATA drive, and it plugs directly into a computer’s motherboard. SATA SSDs are connected via cables. The additional travel distance this adds for the data can increase latency.

3. What are the use cases of PCIe and SATA?

If PCIe SSDs are faster than SATA drives, why wouldn’t you simply opt for the PCIe standard instead? There are some distinct use cases for SATA. For one thing, older PCs and servers may not support PCIe, so if you’re looking to repurpose an older PC, SATA may be your only option. In addition, SATA SSDs are available in 2.5-inch models, while PCIe drives come in a variety of different sizes.

4. How has the PCIe standard changed over time?

While the actual connectivity hasn’t changed (a PCIe 1.0 device can snap into a PCIe 4.0 device and vice versa), PCIe 4.0 SSD is much faster than its predecessor, PCIe 3.0. For example, PCIe 3.0’s throughput is 1GBps per lane, which translates to an overall data transfer rate of up to 32GBps total. PCIe 4.0, however, provides twice the throughput rate per lane that 3.0 does, supporting transfer rates of up to 64GBps.

The Samsung 980 PRO, which is PCIe 4.0 compatible, delivers read speeds up to 7,000MBps, making it twice as fast as PCIe 3.0 SSDs and 12.7 times faster than some SATA SSDs.

Explore more of the differences between PCIe 3.0 and PCIe 4.0 here. Discover how SSDs are addressing government storage needs in this free white paper.

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Karen Bannan

Karen J. Bannan is a veteran business, health, lifestyle and technology journalist with a wide range of publishing experience. Her tech and business work has appeared in Forbes, BusinessWeek Online, Adweek, The New York Times, The Wall Street Journal, MyBusiness Magazine, Government Computer News, Workforce Management, CFO, AdWeek, Crain's New York and Crain's BtoB.

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