Mapping from page table to main memory

In operating systems, there is always a requirement of mapping from logical address to the physical address. However, this process involves various steps which are defined as follows.

1. Generation of logical address

CPU generates logical address for each page of the process. This contains two parts: page number and offset.

2. Scaling

To determine the actual page number of the process, CPU stores the page table base in a special register. Each time the address is generated, the value of the page table base is added to the page number to get the actual location of the page entry in the table. This process is called scaling.

3. Generation of physical Address

The frame number of the desired page is determined by its entry in the page table. A physical address is generated which also contains two parts : frame number and offset. The Offset will be similar to the offset of the logical address therefore it will be copied from the logical address.

4. Getting Actual Frame Number

The frame number and the offset from the physical address is mapped to the main memory in order to get the actual word address.