This historical PC port survived 39 years as a result of it does one factor USB nonetheless cannot

We’ve spent the higher a part of the final couple of many years phasing out legacy pc ports in favor of newer requirements. While VGA and DVI are largely a factor of the previous now, why is it that some relatively costly motherboards nonetheless carry that historical six-pin PS/2 port for connecting keyboards and mice when most peripherals have switched to USB?

PS/2 and USB join the identical peripherals in very alternative ways

PS/2 has far much less occurring beneath the hood

I’m positive that almost all of us who had been round computer systems within the 90s and early 2000s nonetheless fondly keep in mind the previous dependable purple and inexperienced PS/2 ports that we used to attach our historical keyboards and mice.

The port had been accessible for for much longer than that, although, because it launched all the best way again in 1987, when it was first launched on the IBM Personal System/2, which the PS/2 port derives its identify from.

Although it appears a bit like an analog port (suppose: VGA) with its 6-pin design and tubular form, it is truly a digital cable, with every pin devoted to 1 job: knowledge, clock, energy, and floor.

Over time, this old port largely got replaced by the common digital rectangular port that we name USB. You’re in all probability effectively conscious that USB can join much more than simply keyboards and mice like PS/2, which helps clarify why it displaced the previous port so rapidly. PS/2, in distinction, may solely do keyboards, mice, barcode scanners, KVM switches, and a handful of different pretty easy enter units.

This is as a result of they work in essentially alternative ways: PS/2 talks to the motherboard’s keyboard-controller {hardware}, which is usually a part of the Super I/O chip. Super I/O chips deal with quite a lot of low-level motherboard features, together with {hardware} monitoring, fan management, and legacy interfaces like PS/2.

There’s lots of element that we may speak about right here, however probably the most attention-grabbing facet of this setup is that PS/2 works on a {hardware} interrupt foundation — urgent a key or button on the peripheral causes the PS/2 controller to claim an interrupt, forcing the CPU to cease its present calculations and deal with the incoming knowledge earlier than persevering with.

This, after all, occurs in a fraction of a millisecond, which is inconceivable to note.

In distinction, USB is managed instantly by the USB host controller, which could be discovered instantly on the CPU or on the motherboard chipset.

All units share a bus, to allow them to’t simply interrupt the CPU on a whim. Instead, the host controller periodically asks the linked units for brand spanking new knowledge, which is what we seek advice from as polling. At a polling charge of 1,000Hz, the USB host controller checks an interrupt endpoint 1,000 occasions a second.

PS/2 nonetheless has some benefits, however they’re largely for fans

Its benefits are nearly unnoticeable in on a regular basis use

PS/2 has a couple of comparatively area of interest benefits that assist clarify why it hasn’t disappeared from trendy motherboards simply but, although it is normally a single mixed port for the keyboard or mouse as a substitute of two separate ports.

The most evident one is that plugging a keyboard right into a mixed PS/2 port frees up a USB port on the rear for one more gadget. It additionally would not require you to put in any drivers; it is about as plug-and-play because it will get.

Another huge benefit is true N-key rollover assist, that means each single key will get registered when pressed concurrently. Many trendy gaming keyboards assist this too now, however USB’s commonplace boot protocol can solely register six simultaneous non-modifier keypresses.

This was the explanation why many RPG avid gamers like myself most well-liked this old-school port, as these video games generally require lots of simultaneous keypresses that often didn’t register on USB keyboards.

But the actual benefit is PS/2’s independence. Because it generates a {hardware} interrupt when sending a sign, the gadget can stay practical in conditions the place USB utterly fails. It’s notably helpful for excessive overclocking eventualities that may trigger instability, driver lockups, and crashes. It’s a dependable strategy to navigate the BIOS, regulate clock speeds and voltages, save the settings, and hopefully navigate to a profitable benchmark.

That helps clarify why PS/2 is usually discovered on high-end boards just like the Gigabyte B850 GAMING WIFI6 and ROG Maximus Z790 Apex relatively than finances and mid-range variants. There are some exceptions, although. For occasion, the low-end ASUS PRIME H610M-K D4 has a PS/2 keyboard/mouse combo port, which could possibly be helpful in some establishments the place legacy {hardware} and peripherals nonetheless should be supported.

USB has PS/2 overwhelmed in nearly each different approach

It’s merely extra handy and higher for contemporary {hardware}

So we went over the benefits; let’s now concentrate on the drawbacks of PS/2 in comparison with USB.

For starters, it would not assist hot-swapping. If you tried unplugging a keyboard or mouse whereas the PC is turned on, the sudden spike or short-circuit may probably fry the port and, for those who had been tremendous unfortunate, take the Super I/O chip with it. Thankfully, trendy motherboards have fuses that forestall this from occurring, however for those who ever use this port, by no means attempt to hot-swap it.

It’s additionally a significant bottleneck for contemporary high-performance mice and magnetic keyboards, because it’s capped at a tough 200Hz packet ceiling, which feels sluggish on a high-refresh-rate show.

PS/2 has turn out to be out of date with out turning into ineffective

PS/2 is in a uniquely bizarre state of affairs within the PC international stage. For the overwhelming majority of individuals, it is out of date, as they do not also have a keyboard or mouse to plug into it.

However, it solves a particular drawback for a small proportion of hardcore fans who wish to overclock their programs to absolutely the most. And for individuals who have a group of classic keyboards and mice they take pleasure in, it means not having to resort to admitting defeat and utilizing a USB adapter.