Optimization Modes

The SuperCPU has different configurations which allow it to mirror (or not) contents of the 64 or 128's main memory. To explain, one must understand that the 65816 CPU does not act on the computer's internal memory. Instead, it has it's own memory to work from.

When optimization is off, all memory is mirrored. This may cause some delays, specifically due to the fact that the VIC-II chip can not access the memory of the SuperCPU. Therefore, at each VIC cycle (when the VIC has access to the 64/128's memory), the SuperCPU's mirrored memory locations must be copied back to the computer. This obviously takes time and is not always ideal. Graphics intensive programs would clearly be impacted by no optimization. A point that some confuse is this: memory mirroring is bad if you want the best speed performance. When writing programs to take advantage of the SuperCPU, you want to mirror as little as possible.

The SuperCPU has other optimization modes that mirror only portions of memory, for specific applications. For example, to enhance the usage of GEOS, the GEOS screen memory ($8000-$BFFF) is mirrored, but not other locations. There is also a standard VIC mirror mode, and even a BASIC mirror mode, used to mirror the standard VIC-II text screen.