Coursework: Comparative analysis of various addressing systems used in mini and microcomputers.
Main sections of the course work:
1. Introduction. Differences between mini- and microcomputers.
2. The addressing systems used in the mini-computer. (On the example of SM computers).
3. The addressing systems used in the PC (based on the example of a specific PC).
4. The conclusion. Comparative analysis of addressing systems used in mini- and personal computers.
First, consider the simplest methods of addressing, such as register, direct, immediate, and short literal. Registry addressing is difficult to write more than has already been written. Naturally, this way of addressing is supported on both the CM1700 and 80386 processor, as well as by all the processors of the 80x86 family and many other processors that have register memory. Despite the simplicity of this addressing method, it is often used to manipulate registers, clean them, modify their contents. Register memory is very fast, and so most of the computations, especially uncomplicated programmers, are trying to do in these registers. They put the initial values, make calculations, modify and somehow use the results. For all these actions, it is natural to use the register-based addressing method. A great help to the register method of addressing is the direct addressing mode. Of course, it is mainly used to load initial values into registers, known addresses, comparisons with a constant, and so on. But if you dig a little deeper, then this way of addressing gives you many more amenities. For example, to go to a previously known address represented as a segment with an offset, you can use this code:
The RET command takes the values of the segment and offset from the stack, and then makes an intersegment transition. Imagine, the execution of such code without the ability to put on top of the stack a direct value:
mov ax, 0f000h
As you can see, it looks not too compact, in comparison with the previous example, and you can be sure that this is performed for several cycles longer. This is the simplest example of the application of direct addressing, in fact, its application is much broader, especially if work with the operating system is intensively used, where all values, addresses and parameters are standardized and basically known in advance. On the SM 1700, the direct addressing mode is implemented programmatically, using the instruction counter, and in machines based on the i386 it is implemented in hardware. It's hard to say which is better, but the CM 1700 also provides a short literal mode, the advantages of which before the usual direct addressing of data less than 64 are flawless. In the 80386 processor nothing like this is provided, although it may be better - does not increase the command system and therefore simplifies the structure of the processor.
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