CompuServe Messages

To implement VM, you need an MMU. Normally, the MMU goes between the CPU and physical memory. Chip memory is characterized by being the memory that the custom chips access. Since the custom chips do not go through the CPU, they would not go through the MMU either. Consequently, the custom chips' usage of chip memory would not be virtual (although the CPU's usage of chip memory could be). In any case, timing constraints would make normal virtual access of chip memory, i.e., swap to disk, unpractical. But, as long as we are blue skying, it might be practical to have chip memory "swap" or remap to fast memory. You still could not have more memory usable by the custom chips at any given time than they can address, but you could have a large "extended-chip" space that could bring in the memory when needed, possibly even remapping at 60Hz. With the current AmigaDOS, however, this would be a software nightmare. Chris