Comparing USB vs PS/2 Keyboard Performance: Factors and Considerations

The speed of input from a USB keyboard versus a PS/2 keyboard can significantly depend on several factors, including polling rate, latency, and N-key rollover. Understanding these factors is crucial to determine which type of keyboard is better suited for your specific needs.

Polling Rate

In the context of PS/2 keyboards, typical polling rates are between 10-20 milliseconds (ms). This means that the keyboard reports key presses to the computer every 10-20 ms. In contrast, USB keyboards generally offer a higher polling rate. Standard USB keyboards typically have a polling rate of 125 Hz, which equals about 8 ms. Some gaming keyboards can even reach up to 1000 Hz, corresponding to a polling rate of 1 ms.

Latency

Another important factor to consider is latency. USB keyboards can experience slightly higher latency due to the overhead of the USB protocol. However, for most users, this difference is negligible, especially when using high-quality USB keyboards designed for gaming, which minimize this latency.

N-Key Rollover

N-key rollover is a feature that allows multiple keys to be pressed simultaneously without missing any inputs. PS/2 keyboards typically support full N-key rollover, meaning they can handle a simultaneous press of multiple keys reliably. USB keyboards also support this feature, but it can depend on the specific design and quality of the keyboard.

Practical Considerations

While USB keyboards theoretically offer a performance edge due to higher polling rates, the difference in performance is often minimal for typical use cases. For tasks such as gaming or high-speed typing, some users may prefer the PS/2 interface for its reliability and full N-key rollover. On the other hand, USB keyboards are more convenient and often come with additional features, making them a popular choice for general use.

Personal Experience

I regularly use a PS/2 and USB keyboards with my desktop. I use an IBM M-series bucking spring keyboard for regular typing and a cheap Microsoft keyboard when typing on Skype. I have never noticed any significant difference in performance between these keyboards, and my experience highlights that the choice between USB and PS/2 keyboards can be subjective.

Expert Advice and Root-Cause Analysis

Phillip Remaker offers some excellent advice on root-cause analysis. When troubleshooting, it's important to be methodical and rigorously document each step. For example, if you suspect a hardware issue, swapping parts such as the keyboard with a new identical PS/2 keyboard can help isolate the problem. This methodical approach involves replacing parts one at a time and carefully documenting the results.

Remember, the client’s job is to define the problem, not provide a solution. As an expert, your role is to provide the necessary tools and information to help identify and resolve the issue. Once you have solved the problem, don't hesitate to share your findings—reading about how other users solve similar issues can be highly insightful.

Comparing USB vs PS/2 keyboards isn't just about polling rates and latency; it's also about understanding the specific requirements of your tasks and personal preferences. By considering all these factors, you can make an informed decision on which type of keyboard is best for you.