keyboard and mouse

The PS/2 mouse is normally detected/initialized only when the computer is booting up. That is, the mouse is not hot-pluggable and you must restart your computer whenever you add/remove a PS/2 mouse (furthermore, some motherboards may be damaged if you add/remove a PS/2 mouse while the computer is running.)
The initial detection of the PS/2 mouse occurrs during POST. If a mouse is detected, the BIOS will allow the operating system to configure/enable the mouse. Otherwise, it will inhibit communication on the mouse's bus. If you boot the computer with a mouse attached, then detach/reattach the mouse while in Windows, the OS may be able to detect the mouse was reattached. Microsoft tried to support this, but it only works about 50% of the time.

The above info was collected from the website:http://panda.cs.ndsu.nodak.edu/~achapwes/PICmicro/mouse/mouse.html
There is other interesting info at this site on your question.

It could be that the Resource setting for the Keyboard is standard and will not require rebooting,because it is less likely to be sharing IRQ with any other device,unlike the mouse which could be sharing its IRQ,so the motherboard is programmed to require a reboot,this would allow the Resource settings to be detected and specify IRQ so that it is lees likely to conflict with another device.

PS/2 keyboard & ps/2 mouse? They should never be connected when the computer is on. Why? Because doing that tends to short out the connectors if they are inserted crooked or if one or more of the pins in the PS/2 connector get bent. (I've seenwhere people have tried to force in a keyboard and bent pins, essentially ruining the keyboard -- unless the pin can be bent back without breaking).

Most computer detect both the keyboard connection and the mouse connection at POST. If you are having these inconsistent results with the mouse, i would suspect a bad mouse connection or a bad mouse.

If you are using infrared or USB keyboards, then that might also explain the difference. It is not a good practice to connect PS/2 devices when the computer is on. USB/infrared devices can be connected/activated when the computer is on.

I had a Compaq deskpro EN just yesterday that someone had removed the mouse an keyboard while it was running. I plugged them back in and they both worked. Why? I have no idea. Most of the time niether will work. Must be the computer gods at work again. You should never do a hot swap of a ps2 kb or mouse for the reasons above.

The simple answer is that the keyboard is handled in hardware, and is a built in feature of the operating system.
Further, all keyboards conform to a common I/O standard.

A mouse is considered an optional component, and requires a specific driver.

If the installed driver doesn't support the mouse that is plugged in, it will not work.

Since the PS/2 port is handled by Windows like the PCI bus, Windows only searches for hardware on boot.

The USB port on the other hand is polled on a regular basis to look for new hardware.

As a couple of other responders stated, it is hazzardous to the health of both the motherboard and the mouse/keyboard to hot swap PS/2 devices.

If you need to hot swap the mouse and keyboard, switch to USB devices.

Chas

There is also OS concerns to keep in mind. The more modern operating systems can recover if you unplug the mouse (Win2K/XP can, but NT4 cannot). I would think that Win98 possibly could, but I know that Win95 cannot. The more modern operating systemscan keep the drivers for the mouse in memory without getting confused. The older operating systems get confused when you unplug the mouse.
As for the keyboard, the other comments are right on this. Keyboards are maintained on a system level, not really from the OS. That is why you can unplug a keyboard, plug it back in, then press the Caps Lock button to "refresh" the keyboard and get it to work again.
But for the mouse if you want to do this, upgrade to the most recent operating systems. They can do this too (and it is a nice feature!).

hope this helps

The way I understand it is this. The difference has to do with the method and speed with which the data is transmitted. A simplistic way of looking at it is this: The data to and from a mouse is transmitted (almost) immediately, while the data transmission for the keyboard is more or less a “send and wait” signal. If the data transmission is interrupted, the device fails. That’s why the mouse would fail and the keyboard would continue to work. Subsequently, the interfaces for each are designed accordingly. The keyboard/system protocol is different than the mouse/system protocol.

See these links for some very detailed information (if you’re interested.)

PS/2 KEYBOARD & MOUSE PROTOCOLS: Auxiliary Device and System Timings:

http://www.networktechinc.com/ps2-prots.html

Keyboard to system protocol and System to keyboard protocol:

http://members.tripod.com/~ilkerf/c64tower/F_Keyboard_FAQ.html#KEYBOARDFAQ_007

(REMOVE SPACES from the pasted URLs.)

Maxwell

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