Question

Explain how an address generated by a program (such as by a load word instruction) converted to a virtual memory address. You should describe the process and show how this process is sped up

Answer 1

`Hey,

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Memory consists of large array of words or arrays, each of which has address associated with it. Now the work of CPU is to fetch instructions from the memory based program counter. Now further these instruction may cause loading or storing to specific memory address.

Address binding is the process of mapping from one address space to another address space. Logical address is address generated by CPU during execution whereas Physical Address refers to location in memory unit(the one that is loaded into memory).

The run time mapping between Virtual address and Physical Address is done by hardware device known as MMU.

In memory management, Operating System will handle the processes and moves the processes between disk and memory for execution . It keeps the track of available and used memory.

Instruction-execution cycle Follows steps:

1. First instruction is fetched from memory e.g. ADD A,B
2. Then these instructions are decoded i.e., Addition of A and B
3. And further loading or storing at some particular memory location takes place.

As main memory and registers are built into processor and CPU can access these only.So every instructions should be written in direct access storage
devices.

1. If CPU access instruction from register then it can be done in one CPU clock cycle as registers are built into CPU.
2. If instruction resides in main memory then it will be accessed via memory bus that will take lot of time. So remedy to this add fast memory in between CPU and main memory i.e. adding cache for transaction.
3. Now we should insure that process resides in legal address.
4. Legal address consists of base register(holds smallest physical address) and limit register(size of range).

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