PhysP: Physical Pages and Memory Addressing

Study Notes

Physp

PhysP stands for Physical Pages, which is a term used by computer systems to describe how memory addresses are managed and accessed. In some architectures, such as x86 processors, each physical page corresponds to a single hardware addressable memory location, allowing direct access to physical memory. This contrasts with virtual memory systems, where multiple virtual pages may share the same physical page and require translation through a page table.

Physical Addressing

Physical addressing is the process of directly accessing physical memory locations in a computer system. It is the most direct way of accessing memory and is often used by low-level software such as device drivers and boot loaders.

Memory Management

In modern computer systems, memory management is essential for efficiently using the available memory. Memory management units (MMUs) or memory management controllers (MMCs) are responsible for managing and translating virtual addresses to physical addresses. The MMU translates virtual memory addresses into physical memory addresses, allowing access to physical memory by using a combination of virtual and physical addresses.

Virtual Memory vs Physical Addressing

Virtual memory allows a program or operating system to use more address space than is physically available in the computer's main storage. This means that virtual addresses do not directly correspond to physical addresses on the machine hardware. Instead, the mapping between virtual and physical addresses is handled by the page table, which is stored either within the processor itself or in a separate chip called the memory management controller.

On the other hand, physical addressing uses only one level of translation from virtual to physical addresses, allowing for direct access to physical memory. However, this approach often requires rebooting the entire operating system when changing available memory, making it less flexible compared to virtual memory systems.

Physical pages are typically larger units of allocation than standard pages, with the size depending on specifications set by industry consortiums such as JEDEC. For example, x86 physical pages could be 4KB or 1MB in size, while AMD64 physical pages can vary depending on the CPU model.

Summary

In summary, PhysP refers to the use of physical addresses in managing computer memory, where each physical page corresponds to a single hardware addressable location. The difference between physical addressing and virtual memory lies in how they manage and translate memory addresses, with physical addressing providing more direct access at the expense of flexibility and the need for reconfiguration upon memory changes.

Description

Explore the concept of PhysP, which involves managing computer memory through physical addresses. Learn about physical addressing, memory management, and the differences between virtual memory and physical addressing.