Difference Between Physical Address and Logical Address

The major difference between a physical address and logical address is that a physical address is low-level hardware-specific and used by the hardware directly. On the other hand, a logical address is a higher-level, software-friendly address that requires mapping or translation into a physical address before being used by the hardware.

Physical addresses are specific to the hardware architecture and memory layout of a specific computer system. They are not portable between systems or even architectures. Logical addresses, in turn, may be portable and adapted for use on many different systems or architectures, provided that the translation mechanisms of those addresses are compatible.

Table of Content (TOC)

• Tabular Comparision Between Physical Address and Logical Address
• What Are Physical Addresses?
• What Are Logical Addresses?
• Key Differences Between Physical Address and Logical Address

Tabular Comparision Between Physical Address and Logical Address

Here's a tabular comparison of the key differences between physical addresses and logical addresses:

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What Are Physical Addresses?

Physical addresses are addresses that specify actual (real) physical locations in memory. It is a real memory location where the data is stored.

Hardware, such as the CPU and memory controller, can directly access corresponding memory locations with physical addresses, and translation or mapping is not involved.

Here are some key points about physical addresses:

• Physical addresses are low-level addressing modes that refer to hardware architecture and point to a specific computer's memory layout. The hardware uses this mode directly to access memory locations and communicate with devices.
• Physical addressing allows hardware to access memory locations directly. It points exactly to where in the memory data is being written or read.
• It is the map of the fixed and predetermined hardware design configuration and memory, relating the physical addresses to the memory locations.
• The size of the physical addresses is directly proportional to the quantity of physical memory in the system. In lay terms, the size of the physical address space shall be determined according to the total amount of memory installed.
• Physical addresses cannot be moved from one system or architecture to another since they are directly related and associated with a computer system's hardware and memory layout.
• Physical addresses are more effective in memory accessing than logical addresses. This justifies that overhead from translations and mappings of the address is avoided.

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What Are Logical Addresses?

The logical addresses are the virtual addresses of a CPU generated at run time. These do not exist in the memories as physical addresses; they act as pointers for the CPU to access real memory locations. 

Here are some key points about Key logical addresses:

• Logical addresses are addresses used by software programs and operating systems to simplify memory management and provide a more flexible and abstract way of accessing memory or devices.
• Logical addresses are part of the virtual memory abstraction, which allows programs to operate in a larger logical address space than the available physical memory.
• A logical address must be mapped or translated to its corresponding physical addresses before the hardware can use it. This translation is typically performed by a hardware component called the Memory Management Unit (MMU).
• Using logical addresses allows for memory protection mechanisms, where different programs or processes are isolated from each other's memory spaces, enhancing security and stability.
• Logical addresses are generally more portable and can be used across different systems or architectures as long as the address translation mechanisms are compatible.
• The abstraction provided by logical addresses enables features like demand paging, swapping, and shared memory, which are crucial for efficient memory management and resource utilization.

Key Differences Between Physical Address and Logical Address

Here are the key differences:

• The physical address represents the actual physical location of data in memory or devices. In contrast, a logical address is a virtual or symbolic representation of memory locations used by software programs.
• Physical Addresses are generated based on the hardware architecture and memory configuration, whereas the CPU generates logical addresses while a program is running.
• The physical address is used directly by hardware to access memory locations; no translation/mapping is required. Meanwhile, the MMU must translate or map a logical address to its corresponding physical address before hardware can use it.
• The amount of installed physical memory in the system limits physical addresses. On the contrary, logical address can be part of a larger virtual address space, exceeding the available physical memory.
• Physical addresses are tied to a specific hardware architecture and memory layout and are not portable across systems. In contrast, logical addresses are more portable across different systems and architectures.

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