I am going to presume you are using a version of Mandrake.
This is a new one for me.
You should be able to set the resolution for the CLI in mcc [The Mandrake Control Center] / boot / boot manager.
When you get to the screen which shows you the menu choices [linux, windows, etc.], select your linux menu choice, click advanced, select the CLI screen resolution of your choice in the drop-down [MnadrakeLinux 10 Community].
If you use an earlier version of Mandrake, there should still be an option for screen resolution, but it may not be in that screen - but it will be in the boot loader utility.
Sorry I am unable to be more specific, but since I do not know which version of Mandrake you are using, or even if you are using Mandrake at all ...