I have a keyboard that has N-key-rollover.

I can connect it to my computer using USB, but in the package there also was an USB to PS/2 connector I can use to plug in the keyboard via PS/2.

Of course using this PS/2 connector I can remove the 6-keyrol over limitation of USB.

I was wondering how using a PS/2 connector further influences the user interaction and if those changes can be beneficial for gaming.

  • 1
    I've never really understood how converting from USB to PS/2 removes the USB rollover limitations. It seems so strange that it can still get all the functionality through the USB line, as long as it's not the final connection. – JMac Jan 7 '19 at 14:59
  • @JMac The reason for this is that connecting the keyboard with PS/2 means that the computer will use a different protocol for communicating with the input device, as I explained in my answer below. The limit for the rollover is not caused by the actual USB cable, but the protocol it uses. – Bassie-c Jan 7 '19 at 18:19

Modern gaming and PS/2 vs USB

PS/2 is an original way of connecting keyboards (and mice) to computers, before USB was created. Apart from the differences I will mention in this answer, a PS/2 and USB connected keyboard will behave almost entirely the same while gaming.

Different protocols

PS/2 uses a different protocol in dealing with actual user input. When the state of a PS/2 device changes (e.g. a key is pressed/released), the protocol interrupts the current task of the CPU and the system immediately starts dealing with the new state. USB on the other hand gets polled, which means the computer keeps asking multiple times a second the input device for its current state.

The good

  • This difference in protocols can cause a slight difference in speed, but it will be so little that it can be neglected for gaming and other regular uses of a computer.
  • As you mentioned in your question, the difference in protocols also allows for N-key-rollover. But while N-key-rollover means that you will never run into problems, the 6-key-rollover that USB supports is almost always sufficient for gaming purposes. (Try pressing 6-keys at once at your keyboard. You ever did something like that while gaming?)

The bad

  • Because PS/2 interrupts the actual OS, it directly connects to the system. On older system this meant that removing a PS/2 connected device while the system was active could cause it to crash. On most modern system this won't be a problem, but it is still something to keep in mind.
  • Since PS/2 connectors were not designed to be as frequently plugged
    in and out like we are used now with USBs, doing this can lead to bent or broken pins.


So in the end, no, using PS/2 has no benefits for gaming, except for the N-key-rollover that could be useful in some special cases. While connecting your keyboard using PS/2 won't harm your game experiences either, it is probably the easiest to just stick to the protocol everyone uses: USB.


There are other reasons not mentioned in this answer for using PS/2, but these don't make any difference on gaming. For more information I suggest the sources of this answer:


Wikipedia - https://en.wikipedia.org/wiki/PS/2_port

  • Is see this answer is receiving downvotes. Why do you find in not useful? How could I improve it? – Bassie-c Jan 6 '19 at 18:54
  • 2
    PS/2 connections were introduced with the IBM PS/2 computers. Before that (XT and AT pcs) used a 5way DIN connector. So PS/2 was not, strictly, the original connection. – pew Jan 7 '19 at 9:04

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