Early 2009 iMac to DisplayPort

[ks-man]

I have an early 2009 iMac which I'm trying to connect to a new monitor using the mini display port out on the iMac to the DisplayPort input on the monitor. The monitor is not being recognized. I believe the computer originally came with an adapter for the mini displayport to DVI however I'm not sure what happened to that. Should the mini displayport work directly to displayport or is that model too old for that connection?

Thanks.

 

[Significant1]

It should work directly. There never was an adapter in the box (Apple loves selling adapters, not giving them away).