What Are Expansion Slots in a PC? [Explained with Types] (2024)

Do you see several slots on the motherboard’s surface? They’re meant to install a graphics card, sound card, or network card. These slots are called expansion slots. They amplify and extend the system’s capabilities and improve performance.

The expansion slots on Motherboard are often spread throughout, and in this article, I will discuss their types, how to use each to the fullest, how they have evolved in time, and more.

Expansion Slots in PC: Explained

1. Peripheral Component Interconnect (PCI): Even though the standard vanilla PCI slot is a tad dated, it is a good starting point for connecting modems, network cards, and even sound cards.
2. PCIe Express: These lots are the most versatile and known for establishing high-speed connections with sound cards, graphics cards, and other peripherals.
3. M.2 Slots: This is the most modern expansion slot in play, supporting high-speed SSDs. You can even pair Wi-Fi cards and networking adapters with the M.2 slots.
4. U.2 Slots: These are ultra-high-speed interfaces meant for enterprise-grade storage units. Even though the U.2 slots use connectors similar to SATA Express, the transfer rates are higher.
5. SATA Express: These come with high-speed PCIe and SATA functionality via a single connector. These are mostly meant for storage modules.
6. Thunderbolt Slots: These interfaces, especially Thunderbolt 4.0, can support ultra-high transfer rates, going as high as 40 Gbps. They can house graphics cards, displays, and external storage modules.
7. Accelerated Graphics Port (AGP): If slotting graphics cards is your priority, you need to consider the AGP expansion slots, which are a bit old but still relevant to PCs.
8. Industry Standard Architecture (ISA): ISA expansion slots are a kind of ancient entity that used to fit in modems and sound cards. It isn’t easy to find a motherboard with ISA expansion slots.
9. Audio Modem Riser (AMR): AMR slots are old and were meant to lend modem and audio-specific functionality via single-card support.
10. Communications and Networking Riser (CNR): Here is another obsolete expansion slot known for offering modem, audio, and even networking support, via a single card. Like AMR, even CNR slots are now obsolete.

In addition to these slots, you can also add EISA and VESA to the list of obsolete expansion slots. I will discuss them in detail in a bit. Also, there are USB and memory slots, which aren’t usually termed expansion interfaces.

The reason is that these slots do not enhance the PC’s functionality like the USB expansion slot is only meant to fit in peripherals and external devices. Memory slots are meant for the RAM modules and are basic and essential when it comes to simply setting up a PC.

Unpacking Different Slots and How to Use Them:

Now that you have a basic idea of how each slot works, here are the most important ones in detail:

Peripheral Component Interconnect (PCI)

The PCI slot on the motherboard is a lifesaver. It helps bring new hardware elements to your PC, including network adapters, sound cards, and peripherals. If you are interested in PCI origins, the slot came in 1990 and has been around since.

Coming to the PCI types, the most common variant is the PCIe or the PCI Express slot. Most modern motherboards have PCIe slots, facilitating extremely fast data transfer speeds.

As for the sub-categories, you can pick motherboards with PCIe 1.0, 2.0, 3.0, and even 4.0 slots. As for sizes, you can pick the following versions: x1, x4, x8, and x16.

In case you are into specifics, the smallest PCIe slot, or the x1 is suitable for smaller modules like network adapters and sound cards. They support a transfer rate of up to 250 Mbps.

The x16 versions are the largest and support high-performance graphics cards, capable of supporting data transfers at 16Gb/s.

And finally, as I mentioned, PCI slots support sound cards and network adapters that can take your PC’s audio and internet performance to the next level.

You can even consider pairing TV tuners with PCI slots, but nothing beats the union on PCIe slots and graphics cards. The newest motherboards and prospective PCs requiring the most high-end GPUs have PCIe 4.0 as the choice of PCIe slot, boasting 16 lanes and even 64Gb/s of data transfer bandwidth, back and forth.

Accelerated Graphics Port (AGP)

Well, the AGP is a near-obsolete slot that came to be in 1990. AGP slots are meant to house high-performance graphics cards. However, PCIe slots have majorly replaced AGP slots in modern-day motherboards and computers.

As for the role, AGP slots offer high-speed (up to 2.1Gbps) data transfer interfaces between the GPUs and the entire computer system.

AGP slots were only meant to nestle the GPUs and not anything else. You could get motherboards running different AGP variants when they existed, namely 1x, 2x, 4x, and even 8x.

Industry Standard Architecture (ISA)

The ISA slots are now archaic and ancient. They were extremely popular when PC motherboards used to be hefty, especially between the 1980s and 1990s. AGP and then PCI slots erased ISA slots from existence.

Coming to usage, they were meant to expand the capabilities of the machine to sound cards, modems, and even network cards.

They had a typical data transfer rate of 8 to 10 Mbps. However, their primary job was supporting legacy devices that couldn’t work with the newer slots. This feature kept the ISA slots popular even through 1995.

However, the slower data transfer rates were reasons big enough that the PC builders started looking elsewhere. Plus, they could only support 16-bit PC devices.

Universal Serial Bus (USB)

The USB slot isn’t typically meant for serving as an expansion interface as USB slots are the basic necessities and not a way to amplify PC performances. As for the origin, USB slots came to be in 1996 and have been going strong since.

Coming to the utility, they are meant to connect external hard drives, printers, keyboards, mice, and other peripherals. Also, with USB slots in play, you need not power down the PC to connect new devices or peripherals.

USB slots come in different versions. For instance, USB 2.0 surfaced in 2000 and supported data transfer rates of up to 480Mbps. There is USB 3.0, or the SuperSpeed USB version, with a data transfer rate of 5Gbps.

It is important to note that the USB 3.0 versions extend to USB 3.1 and USB 3.2 — boasting higher transfer speeds.

Memory Slots

Memory slots, like the Universal Serial Bus slots, aren’t usually termed expansion interfaces. Instead, they are your typical RAM slots that are useful for including RAM modules for basic PC operations.

The only time they become useful as expansion interfaces are when you plan on adding more RAM than the existing number. You might consider pairing more RAM for CAD and several other memory-intensive apps.

Coming to memory slots, the most common ones include DIMM and RIMM slots. DIMMs, or Dual In-Line Memory Modules, are found in modern motherboards. RIMM or Rambus In-Line Memory Modules are older RAM standards.

Surprisingly, RIMM slots’ speed and data transfer rates are higher than DIMM slots.

As for compatibility, you must ensure that the RAM modules you insert are compatible with the motherboard slots. Do note that installing incompatible RAM modules can damage the PC.

List of Outdated Slots

Here are some outdated PC expansion interfaces that have been replaced:

1. CNR slots: These outdated slots cater to audio and networking devices/peripherals. Over time, they were replaced by USB and PCIe slots.
2. AMR slots: Audio Modem Riser slots had “modem” in their name, which explains why they were so popular for integrating modem-specific peripherals and audio-centric devices. They, too, were replaced by USB and PCIe slots.
3. VESA slots: VESA slots, or the Video Electronics Standards Association slots, were local bus modules meant for video devices. Over time, the PCI and AGP slots erased VESA interfaces from existence.
4. ISA slots: The Industry Standard Architecture slots were designed to connect legacy peripherals. While efficient, PCI and PCI Express slots replaced them in time.
5. EISA slots: The Extended Industry Standard Architecture slots worked as ISA slot expansions, also meant to connect peripherals but with better data transfer rates than the ISA counterparts. They were replaced by PCI and PCIe slots.

Frequently Asked Questions

Conclusion

Overall, I covered most modern and legacy expansion interfaces that you can find on a computer or, rather, a motherboard. I hope, by now, you have a clear understanding of them. If you still have any doubts, please ask them in the comments below.