How can I tell which version of PCM I have ?

[sjr-997]

I'm looking into the Sat Nav DVD update, and it says on the Porsche website, for MY05 or cars with 2.1 PCM.

My car was registered Jan 2005.

Any idea if the car can tell me which version it has ? Is this important ? Does the new DVD just update the car's software ?

I currently have the 10/2004 DVD in the car's sat nav.

cheers

Simon