NXP LPC project: Configure RAM usage

Hi

When i make a new empty project for LPC2368, and build it, the total RAM use is 3 kb / 9%, because total RAM is set to 32kb,

But this is not completely true: The LPC2368 has 32kb general purpose RAM, 16kb for Ethernet/general purpose, and 8kb for USB/general purpose.

The question is: How do I decide what these RAM area's should be used for? How can I use the Ethernet/USB RAM as general purpose?

I know I have worked with this a long time ago, but I simply can't remember... Something with a memorymap XML file ???

Thanks!

Kåre