I see my lecturer in the lab are using 2 CPU unit on 1 monitor. I notice because both of his cpu have different item at desktop (But at any time, he can only use 1 desktop ) , so i go curi look at his pc when he not around. It really 2 PC connect to 1 projector .

The projector has 2 inputs or more. Usually projectors have this function (for easier presentation). There's a control to switch between 2 inputs.

i think if u type KVM in google search u may find ur answer, an intermediate hardware where your monitor, keyboard & mouse connected to this KVM things, and all cpu be it either 2, 4 or more CPU connected to this KVM. So there is a button for every cpu connected so that u can select the button on which cpu u want to use....i hope this is the thing that u might refer to...

There is such a thing as CPU or monitor switcher. Its a desktop size item that you could put 2 CPU or more or more. And switch the display real time. Can get in low yat also.

The usual way is to have multiple monitors per PC system. For this to be possible, you need a GPU with more than one VGA output or DVI output. Another way is to have two or more GPUs in one PC system. And, of course, you need more than one display monitor. This is single PC multi-monitor setup.

The display mode that you have seen can be or is called the multiple desktops mode (one separate desktop per one display).

There is also the clone mode where one or more displays have the same copy of the desktop area.

There are other desktop mode like spanning one single desktop across multiple displays (all monitors span the whole desktop area).

All those modes can be applied on Nvidia cards through Nvidia's nView Desktop Manager from its Nvidia Control Panel system tray.

I am not sure about ATI cards.

Multiple PC multi-monitor setup is not commonly applied but it is possible. However you need a specialized software to do just that. There are commercial and open-source versions of this type of software.

See http://en.wikipedia.org/wiki/Multi-monitor

Yes, someone has just mentioned about the KVM switch technique.

Damn i just found out this thing is possible today. Guess i can setup as many pc i want with single LCD
Anyway thank guys, i found my answer here already

Newer LCD Can Support 3-4 Input..

DVI, S-Video, HDMI, VGA

Yes, the KVM switch will make possible the multi-PC single-monitor setup.

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Dell 2707 LCD

You Can Have Dual Display At The Same Time..