What Is a PS/2 Port and Why Do Some Computers Still Have Them?

The venerable PS/2 port first showed up in our lives in 1987, and it has mostly been superseded by USB. So why do some modern computers still have it?

Modern gaming PCs are equipped with lots of great modern connectors. We have USB-C ports, DisplayPort/HDMI ports, and... a PS/2 port? This legacy connector looks like it belongs in the 80s or 90s, and indeed, it probably does. Yet, a lot of modern systems and motherboards, even gaming systems equipped with the latest AMD Ryzen/Intel Core chips, seem to insist on digging this old connector out of its grave. And while it might not make sense to you, or to a lot of people, there are reasons why it's there.

Why are some modern PCs still including this old port?

What Is a PS/2 Port?

Before we can dig into why these ports are still around these days, we first need to understand where they originated.

It was the year 1987. IBM used to have a stronghold on the PC market in years past, but thanks to the rise of IBM PC clones that could use IBM software and hardware, that market dominance quickly disappeared. In an attempt to recapture it, IBM also wanted to make sure clones couldn't be put together as easily and developed a line of machines with a proprietary expansion bus and operating system, which it called the Personal System/2, or PS/2 (no, not a PlayStation 2).

IBM's wishes to regain its former glory didn't materialize with the PS/2, but the lineup did leave a lasting legacy, as computing innovations like the 3.5-inch floppy disk and the VGA video standard actually had their headstart on the PS/2. It also gave birth to the PS/2 port.

The PS/2 port replaced both the DIN keyboard connector and the DE-9 mouse connector, and it allowed for a simpler way to connect a mouse and a keyboard to a PC. While it was first introduced with its namesake PC lineup, it would go on to be used on non-IBM computers as well, becoming the standard before USB eventually took over as the favored port for peripherals.

Back in the day, computers would normally come with at least two PS/2 ports—one for the keyboard, and one for the mouse. They would also be color-coded, with the keyboard port painted blue and the mouse port painted turquoise/green. Most systems including PS/2 ports these days will come with a single PS/2 port where you can plug either a mouse or a keyboard, or use a splitter to connect both (in a similar color-coded manner). Others will still opt for a full set of two ports.

Why Are PS/2 Ports Still a Thing?

Now that we're a bit more familiar with PS/2 ports, it's time to address the elephant in the room. If this port was introduced in 1987, was prevalent over the 90s and early 2000s, and is all but gone from most people's lives, why do some motherboards still include one?

The ASUS ROG Maximus Z690 Apex, a +$800 motherboard with support for 12th Gen Intel Alder Lake chips, DDR5 RAM, and PCIe 5.0 connectivity, notably includes a complete set of two color-coded PS/2 ports. It's got to be good for something, right?

Image Credits: ASUS / Newegg

PS/2 has been mostly superseded by USB for several years, but there are a few differences to the way both standards work that makes some folks swear by PS/2 ports well into the third decade of the 21st century.

The way USB peripherals work is that the computer will constantly check on them multiple times per second (a process known as polling) to see if they're idle, moving, or doing something. PS/2 peripherals, on the other hand, can actually take the lead on that, as they're able to send an interrupt to the CPU whenever they're doing something. If you move your mouse or click something, your mouse will directly communicate with your CPU to register the action, rather than waiting for the computer to notice. This means, in most cases, there is less latency than with a similar USB peripheral because it's not polling but actively interacting with your computer.

They also have other advantages. In the case of keyboards, PS/2 opens the possibility of true N-key rollover, meaning you can press down on however many keys you want, and they'll all register. If you reboot into your BIOS, there's a chance your USB peripherals will not be recognized, whereas you won't have that issue with PS/2 peripherals since they're all universally compatible.

These advantages, or rather technical differences, have led some pro gamers to hold onto their PS/2 peripherals. While most of the differences I've mentioned early might be virtually imperceptible to most people (we're talking mere milliseconds here), having lower latency can benefit some folks regarding competitive gaming and esports. Whether it's justified, though, is another story—it's generally accepted that you're probably better off buying a superb gaming mouse than holding onto your old ball mouse from 1999.

We won't judge you for wanting to keep your Model M keyboard in use, though.

Should I Use PS/2 Peripherals, Then?

No, you shouldn't. Well, probably not. There's a reason why USB was developed, after all.

We didn't go over PS/2's disadvantages, but it has many. For one, unlike USB, it's not a hot-swappable port—if you unplug your mouse or keyboard from a running system, you'll need to reboot for it to work again, and worse, you could even damage it. The port itself is also quite fragile, and you can easily bend the pins inside a PS/2 connector if you're not careful with it.

Unless your specific use case absolutely demands the use of PS/2, there's no reason to use it. You might think your ball mouse and your old keyboard might be ready for a non-ironic comeback, but it's better to leave the past in the past.

There's a Demand, But It's Probably Not Justified For Most People

We can see the reason why some motherboards still include this old port. Some people swear by them and refuse to make the move to USB because they feel that, for their specific use case, PS/2 is superior. A market is there, and while it's a minority, it's a very loud one. And while for some scenarios that might be true, for most people, USB peripherals are the superior option.

Hopefully, now you know the difference.