How can garbage collectors be faster than explicit memory deallocation?

Question

I was reading this html generated, (may expire, Here is the original ps file.)

GC Myth 3: Garbage collectors are always slower than explicit memory deallocation.
GC

Answer 1

One approach to make GC faster then explicit deallocation is to deallocate implicitly :

the heap is divided in partitions, and the VM switches between the partitions from time to time (when a partition gets too full for example). Live objects are copied to the new partition and all the dead objects are not deallocated - they are just left forgotten. So the deallocation itself ends up costing nothing. The additional benefit of this approach is that the heap defragmentation is a free bonus.

Please note this is a very general description of the actual processes.