@Bandolin - to address more than 4GB you need 64bit CPU - which the G5 is... The Intel Dual Core isn't, so 4GB would be the maximum (I guess possible when 2GB modules appear). So I rendered another image and this is whatI got: CPU: 98.9% utilisation Real Memory: 241.26MB Virtual Memory 946.75MB Now, I cannot hear the disk working at all and the Activity Monitor shows spikes for data reads only - so does Mac OS X go to spare memory for its VM space first? I'll poke around Apple's Dev site I think... Garry