PS/2 vs USB

What is a PS/2 port?

The PS/2 port is a 6-pin mini-DIN connector used for connecting keyboards and mice to a PC compatible computer system. Its name comes from the IBM Personal System/2 series of personal computers, with which it was introduced in 1987. The PS/2 designs on keyboard and mouse interfaces are electrically similar and employ the same communication protocol.

PS/2 is now considered a legacy port, with USB ports now normally preferred for connecting keyboards and mice. This dates back at least as far as the Intel/Microsoft PC 2001 specification of 2000.

What is a USB port?

USB (abbreviation of Universal Serial Bus) is an industry standard that establishes specifications for cables, connectors, and protocols for connection, communication, and power supply between personal computers and their peripheral devices. It was released in 1996. The USB standard is currently maintained by the USB Implementers Forum (USB IF). USB was designed to standardize the connection of peripherals like keyboards, pointing devices, digital still and video cameras, printers, portable media players, disk drives and network adapters to personal computers, both to communicate and to supply electric power. It has largely replaced interfaces such as serial ports and parallel ports and has become commonplace on a wide range of devices. USB connectors have been increasingly replacing other types for battery chargers of portable devices.

There are four types of USB port available -

USB 1.x - Released in January 1996, USB 1.0 specified data rates of 1.5 Mbit/s (Low Bandwidth or Low Speed) and 12 Mbit/s (Full Speed).

USB 2.0 - Released in April 2000, adding a higher maximum signaling rate of 480 Mbit/s (High Speed or High Bandwidth).

USB 3.x - Released on 12 November 2008, provides for a transfer mode at a nominal rate at a 5 Gbit/s (625 Mbyte/s) signaling rate with 8b/10b encoding, the raw throughput is 500 Mbyte/s.

USB Type-C - It was developed around the same time as USB 3.1 and is a reversible-plug, 24-pin, double-sided connector for use with USB devices.

Differences between PS/2 and USB port

If some misconfiguration will happen in BIOS, you will only able to use the keyboard after the OS has finished loading. So, you can't press F2 to correct the BIOS. The solution is to use one PS/2 keyboard.
Some operating systems just won't work with USB keyboards or mice. Furthermore, some operating systems may not have the right USB drivers available during installation which could cause problems with OS installation. On the other hand, PS/2 can be helpful when restoring damaged operating systems which "hang" during a certain part of the boot process. The required PS/2 drivers are much simpler to work with and can be loaded at much earlier stage than USB drivers.
PS/2 KVM switches are easier to design and cheaper to manufacture.
PS/2 connector itself is relatively small, not very difficult to use and it is sufficient for keyboard and mouse use. As far as response times are concerned, PS/2 actually has an advantage over USB devices.
Ps/2 supports sleep waking if your computer under sleep mode pressing key from ps/2 will wake it which is not supported by USB.
Ps/2 directly connects to the motherboard short distance to motherboard whereas in USB it first connects to a bus which is then connected to the motherboard at a long distance from the processor.
PS/2 is also interrupt based, meaning that the signal will not have to wait for its turn. In most cases, the time lost is so low that you won't notice it.
The PS/2 interface provides no restriction on key rollover.
Due to the design of USB, it's easily hot-swappable. On the other hand, PS/2 is not natively designed to be hot-swappable, in some situations unplugging and replugging a PS/2 device into the computer will render it unusable until the system is restarted. This is not always the case, however, if the system drivers recognize the device then this will not be an issue.
USB is the much more popular interface in modern devices than PS/2.
PS/2 supports full NKRO. In contrast, USB is not as compatible with NKRO.
With USB, sometimes has issues with BIOS or waking up from sleep.
USB is hardly new, and the PS/2 standard is far from dead.
The USB standard is also used to connect devices like external hard drives, flash drives, microphones, joysticks, and cameras.