6.0 - Default min and max heap sizes

According to this:

http://java.sun.com/javase/6/docs/technotes/guides/vm/gc-ergonomics.html

as of version 6, the initial heap is set to be 1/64th of the machines physical memory and the max is set to be 1/4th of the machines physical memory.

I was wondering, is the dependent on theavailable memory, or the overall physical memory? i.e. if you have 1gb of physical memory, but half of that is in use, is the max heap size calculated on the 1gb you have or the 512mb you have available?

[518 byte] By [TimSparqa] at [2007-11-27 11:45:36]