7.7.1: Redirect to another display port

[zvivered]

Hello,

I'm booting a board with 7.7.1

This board has 3 DVI display ports, one of them is converted to VGA by hardware.
The board has only one graphic card.

After booting, I can see few boot messages on the VGA output and then, the screen is black.
The display probably goes to another port.

How can I specify the required port in knoppix ?

Thank you,
Zvika