Before, most computer accessories could plug and play via a USB port, and keyboards and mice connected via a PS2 port. Despite being almost entirely replaced by USB, the PS2 port is still a part of many gaming motherboards and computers, but why?

Motherboards still come equipped with PS2 ports for several reasons. They allow for better connection and work well with BIOS. The gaming community also prefers them for added speed due to lower latency. Old keyboards still need a PS2 port, so most manufacturers include it.

Here are the main reasons PS2 ports are on some modern motherboards:

Compatibility: Motherboards with a PS2 port will still have USB ports that are compatible with both old and new devices.
Serious gamers’ preference: Mice and keyboards connected via PS2 ports are considerably faster. Although the difference might seem negligible, it’s crucial in high-processing activities like gaming.
No issues using BIOS: Sometimes, USB-connected peripherals are not recognized when running a PC in BIOS mode, which PS2 peripherals have no problems with.
USB ports can be disabled: Some commercial computers disable USB ports for security purposes, leaving peripherals to the PS2 port.

What Is a PS2 Port?

The PS2 Port (Personal System/2) port was invented in 1987 when personal computers were steadily increasing in popularity. It was first introduced with IBM’s Personal System/2 series, which explains the name.

The port is easily identifiable as a 6-PIN mini-DIN circular port color-coded purple for the keyboard and green for the mouse. Usually, there is an additional small icon of either the keyboard or the mouse in the top-right corner of the port. It is also sometimes known as a keyboard port or mouse port.

Note that while the keyboard PS2 and the mouse PS2 are virtually identical, they usually cannot be used interchangeably. This is because the drivers for the peripherals are programmed to use their designated PS2 port.

PS2 Port Uses

Now, let’s take an in-depth look at the various uses of PS2 ports, which lead manufacturers to include them as a feature on many modern motherboards.

Low Latency Gaming

In the world of competitive gaming, every millisecond counts. High-end gaming accessories are valued for their lower latency. PS2 ports allow users to connect a keyboard or mouse to their laptop with considerably lower latency when compared to USB-powered peripherals.

To further illustrate, a PS2 keyboard communicates directly with the motherboard. On the other hand, a USB keyboard communicates with the USB port, which involves a lot of waiting (more on that below). While the difference between the two is probably a few milliseconds, many gamers prefer a PS2 setup for the lower latency.

However, a good PC setup with a high-tech gaming mouse and keyboard would achieve the same results on a USB port. So, should you ditch your gaming keyboard and mouse and switch to an old-school alternative? It depends on your other preferences, and there is no right answer to that question.

Low Polling Rate

The way USB and PS2 ports communicate with peripheral devices is a major difference. A USB port has a high polling rate. Polling is a process whereby the port initiates a connection with the device to check for any changes and register them.

USB ports are continuous ‘polling’ devices at regular intervals. The default rate is usually 125 hertz. On the other hand, a PS2 port has a default polling rate of 100 Hz. Still, PS2 ports do not need polling to register changes made by the device because there is a direct connection between the peripheral device and the motherboard.

A PS2 mouse is considered to have zero latency because polling is not required to function properly. A PS2 port requires significantly less CPU power to run a peripheral device when compared to a similar device running via USB.

However, this difference is negligible nowadays as modern processors are fast enough to handle the additional CPU load.

N-Key Rollover

One major advantage of using PS2 keyboards is worth mentioning, which is true N-Key rollover. This term describes how a keyboard registers key presses, even when pressed simultaneously.

Older keyboard models that used a PS2 connection guarantee that all the keys will be registered in the order they were pressed. Modern keyboards that run on USB risk missing some of the keys.

Again, this difference may seem minor in the context of the mainstream use of personal computers and keyboards. However, programmers, gamers, and others who require more out of their keyboards might need true N-Key rollover to ensure that all their pressed buttons are registered.

BIOS Compatibility

The BIOS runs the devices before a computer’s operating system is installed. USB keyboards might not always run on BIOS because the computer fails to make the switch when there is no operating system. Using a PS2 keyboard helps communicate with the hardware through BIOS without worrying about having an operating system.

This advantage may not be useful to the average computer user. Still, it is important for repairing computers and for anyone who needs to program a computer to meet their specific requirements.

Old-School Mechanical Keyboards

Even as new keyboard models are coming out daily, some people (gamers in particular) still favor mechanical keyboards. You may have noticed that older keyboards typically have larger buttons requiring more force.

The buttons of a mechanical keyboard each have their own individual switch and spring, which contrasts significantly with modern (non-mechanical keyboards). They typically have a rubber membrane lying beneath all the keys, so less force is required when typing.

Advocates of new keyboard models will say that typing is significantly more comfortable, quieter, and faster. On the other hand, those who prefer mechanical keyboards claim that the pressed individual keys make the typing process more specific and, thereby, easier.

Old-school keyboards were mechanical and connected to the computer via a PS2 port. They are typically more sturdy than the newer models, and many gamers prefer that. Some people even prefer mechanical keyboards for typing or programming, even if they aren’t particularly ergonomic.

They usually claim the sound and feel of the keys are different. Some high-end mechanical keyboards allow users to customize their typing experience. All this is to say there is still a good reason to include a PS2 port, if only for the nostalgic effect.

Better Compatibility

A motherboard with a dual-capable PS2 port for a mouse or keyboard.

Generally speaking, motherboards with a PS2 port will also include several USB ports. This means that the motherboard would be compatible with both types of devices requiring the PS2 port and those that do not.

Companies are increasingly looking towards making universally compatible products, which is one important reason that compels manufacturers to include PS2 ports on motherboards, even if USB largely supersedes it.

If your computer does not have a PS2 port, the only way to connect an old-school keyboard or mouse would be to use an adaptor, which is not always ideal. There is always a higher probability of latency issues with the adaptor or other errors that may cause the peripheral device to malfunction.

Still, some manufacturers go the opposite route and do away with all ports except USB.

More Room for Other USB Peripherals

The universality of USB ports means they are used by millions of devices daily. From microphones to memory sticks, there is an abundance of devices that can be connected to a USB port. However, not every PC setup has enough USB ports to connect the various USB peripheral devices.

Using a PS2 port means freeing up the existing USB port to be used by other peripherals where no other option is available. You may have seen USB routers sold online as a solution to the lack of available USB ports. While this is a short-term solution, you can expect more latency across all the devices plugged into the router.

To circumvent this latency issue, plugging your mouse and keyboard into their designated PS2 ports would free up at least two USB ports that you can use to power other peripheral devices you might need to use.

Disabling USB Ports

Last but certainly not least, some organizations need an added layer of security, so they require their USB ports to be disabled. USB ports are nearly ubiquitous, especially in file storage systems such as flash drives (memory sticks) and hard drives.

To avoid the potential damage a virus-infected USB stick might cause, some organizations have decided to completely disable the USB ports on their computers. This tactic keeps company data from being leaked and prevents the spreading of harmful computer viruses.

In that case, the PS2 port allows the company to use PS2 keyboards and mice as an alternative.

Legacy-Free PCs

Because the PS2 port is considered a legacy and almost entirely obsolete, some manufacturers do away with it. That means legacy-free PCs are available, albeit more difficult to find.

You may wonder what the advantage of designing a motherboard without a PS2 port would be. Here are a few:

Freeing up space for other ports: There is only so much you can add to a motherboard because space is finite. Removing a PS2 port gives the manufacturers added space for other (more useful) ports.
PS2 ports cannot evolve: There is no way of upgrading PS2 ports, so eventually, every other option is faster, and there is no reason to hold on to them.

Should You Use a Legacy-Free Motherboard?

Legacy-free motherboards or PCs are manufactured without any legacy ports. That means they exclude the following (and many more):

Centronics parallel port (used for printers, scanners, etc.).
Serial port (used for console and modem).
Game port (used to connect MIDI and joysticks).
PS2 port (keyboard and mouse ports).
VGA (used to connect to older display units).
Floppy drive (used to run floppy disc drives).
Parallel ATA (connects to the hard drive (fixed, internal), CPU).
IEEE 1394 (connects to external storage).

It depends on what you’re using the motherboard for. For the average PC user, there is practically no difference between a legacy-free PC and a normal one. However, you may need more space on the motherboard to build a PC for gaming, programming, graphic design, or other intensive processing tasks.

For example, to add more processing power to the motherboard, many graphic designers may add additional RAM and a GPU to their motherboard. Using a legacy-free PC allows those users to control what is added to their computers.

In reality, most modern motherboards have extra space for such additions, but it’s possible to access more space using a legacy-free PC.