Why is the memory of 80486 system segmented? What is the principle of segmentation?

The address line and data line of 80386 and 80486cpu are 32 respectively, which means that the maximum storage address space accessed by cpu in real mode is 2 32 = 4 GB. So what if the starting address of the address I want to visit exceeds 4GB? What should I do? Is there nothing I can do?

In order to solve this problem, the protected mode is mentioned here, in which programmers can get more storage address space (that is, virtual address). Therefore, for 80286, the offset is 16 bits, and the maximum size of each segment is 64KB, and the available virtual storage space is1GB (2 30 bytes). For 386 and 486CPU, the offset is 32 bits, with a maximum of 4GB per segment. The available virtual storage space is 2 46 = 64 TB. It is this principle to segment the memory in protected mode, which is also a more effective and convenient method to manage the memory. There is also a more advanced paging management mechanism than segmentation management. Of course, this is another story. (This is similar to register indirect addressing, but slightly different).

If you don't understand, I suggest you read some basic books and principled things. This book "Principles of Microcomputer" seems good, hehe. I hope it helps you.