64-bit processor Definition

The 64-bit processor must have the following points:

1. Complete 64-bit registers

2. Complete 64-bit commands

3. In terms of memory addressing, in theory, a 64-bit processor should have a 64-bit addressing capability, that is, it can address such a large space as the 64-power of 2, however, in actual hardware implementation, this is not exactly the case. For example, AMD's athlon processor cannot be addressing as high as 64-bit, so opteron and itanium can both be used.

In addition, the 64-bit processor can address the 64 power of 2, because the pointer is changed from 32-bit (4 bytes) to 64-bit (8 bytes, the physical address that can be expressed will naturally become the 64 power of 2.

 

 

4. When we say whether a CPU is 16-bit or 32-bit, it refers to the width of the "arithmetic logic unit" (ALU) in the processor. Therefore, this can also be used as a basis for whether a CPU is 64-bit. In addition, the data line section in the system bus, known as the "Data Bus", usually has the same width as ALU (with exceptions ). What about the address bus width? The most natural idea is that the address bus width is consistent with that of the Data Bus. However, in the early stages of CPU, such as 8-bit CPU, if the address bus is also 8-bit, then the addressable memory would only have 256 address units, which is obviously not enough! Therefore, the width of the address bus is different from that of the CPU. This explains some things mentioned in the post above.