System 7: Use of Virtual and Physical Memory

When using System 7, why can systems that are not 32-bit compatible access 13 megabytes of virtual memory, but only 8 MB of physical memory?
The memory map in a 24-bit system only allows for 8 MB of RAM, 6 MB NuBus, and 2 MB ROM and I/O. Virtual memory will use the allocated memory of a NuBus card that is not in use. If you were to put more physical RAM in a Macintosh II running in 24-bit mode, the system would use only 8 MB, and the rest would be ignored.
Published Date: Feb 18, 2012