6.8.0.x, 64 bits, and memory profiling

Hi, I'm using heap profiling on AMD64, and I am getting some slightly strange results. Running the profiling, 'top' shows about 600Mb in use, but the resulting profile shows ~80Mb. Rerunning with -M200M results in an out-of-memory error. Could it be that the profile is calculated incorrectly for 64bit systems? -k -- If I haven't seen further, it is by standing in the footprints of giants