Can any USB mouse or keyboard be connected to the PS/2 connector of a motherboard via USB-PS/2 adapter?

IS there a necessity for the mouse to know a different protocol or a different pinout to be able to be connected to a PS/2 port ?

Many vendors provide USB - PS/2 adapter, but some don't.

From what I know PS2 and USB interfaces even have a different number of pins. How would such an adapter work ?

Will the device have the same performance as before ?

Is it necessary for the USB device to 'know' it is connected to a PS/2 port ? I suppose it is necessary since USB to PS/2 adapters are just that : adapters. not converters. They do not do anything to the signal so probably the keyboard or mouse should know and adapt their signal accordingly.

And another question: Is there any latency added when connecting a USB keyboard or mouse to a PS/2 port using an adapter ? I suppose the adapter itself does not add latency since it only connects some pins to some others, but inside the mouse or keyboard something has to change. The mouse has to switch to PS/2 data serialization instead of USB. In theory PS/2 should be faster but I am thinking that if that particular device is made to work naitvely on USB it could have sort of internal signal converter which may generate some latency.

These adapters are purely mechanical. There is no converter or whatever inside. So, yes, the mouse/keyboard needs to do PS/2 by itself.

Whether the controller IC inside the input device will perform worse with PS/2 will depend on how the protocol switch is made.

It is unlikely that PS/2 will perform noticably different than USB. From just looking at the connection specs, USB is vastly superior, both in speed and latency. Only USB host controller inefficiencies could lead to a worse overall experience.

PS/2 and USB share some properties that make an adapter feasible:

• 5 V
• Low current
• 2 “data” wires (though one is clock on PS/2).
• (two pins on PS/2 are unused)

I can definitively answer the first part of the question,

"IS there a necessity for the mouse to know a different protocol or a different pinout to be able to be connected to a PS/2 port ?"

The answer is yes, a USB HID device (mice and keyboards) must understand the alternative PS/2 protocol in order to function in PS/2 port using USB-PS/2 adapter.

Not every USB mice or keyboard support the PS/2 mode. Presence of the green adapter in the OEM package warrants this compatibility, but the opposite is not true - some HID devices do support PS/2 mode even if the adapter is not included with the product, some don't, all depending on IC in use. For example, the Microsoft Notebook Optical Mouse P/N: X08-86056 does not work in PS/2 port.