| Storing a word into memory The procedure of writing a word into memory location is similar to that for reading one from memory. The only difference is that the data word to be written is first loaded into the MDR, the write command is issued. As an example, assumes that the data word to be stored in the memory is in register R1 and that the memory address is in register R2. The memory write operation requires the following sequence:
- In this case step 1 and step 2 are independent and so they can be carried out in any order. In fact, step 1 and 2 can be carried out simultaneously, if this is allowed by the architecture, that is, if these two data transfers (memory address and data) do not use the same data path. In case of both memory read and memory write operation, the total time duration depends on wait for the MFC signal, which depends on the speed of the memory module. There is a scope to improve the performance of the CPU, if CPU is allowed to perform some other operation while waiting for MFC signal. During the period, CPU can perform some other instructions which do not require the use of MAR and MDR. |
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