Amigas have two types of RAM. Chip RAM and Fast RAM. Original, unexpanded models only have Chip RAM. By expanding your Amiga with some expansion card you can add Fast RAM to it but not Chip RAM. Chip RAM can be accessed by both CPU and Chipset. Fast RAM can be accessed by the CPU only. All graphics and sounds have to be kept in Chip RAM since in order to display/play them they must be accessed by the Chipset. On the other hand, the expandable Fast RAM is much faster since only CPU will be ever accessing it so it doesn't have to wait for the others. Running programs and their (non-media) data are kept in Fast RAM. If you don't have any Fast RAM, everything is kept in Chip RAM.
