segment:offset寻址方案如何工作? [英] How does the segment:offset addressing scheme work?

问题描述

我读到，在Intel 8086 CPU时代，最大的寄存器是16位，每个人都在寻找一种方法来访问超过65536字节的线性内存，但他们没有扩展CPU寄存器，而是发明了该段:offset寻址方案以及据我所知，您可以将两个16位寄存器组合"成一个32位内存地址.但是在同一地方，我也读到了CPU只能访问1MB的内存.这是如何运作的? 2 ^ 32等于4,294,967,296，所以我不明白，请赐教:)

I've read that in the days of the Intel 8086 CPU the biggest registers were 16-bits and everyone were looking for a way to access more than 65536 bytes of linear memory but instead of expanding the CPU registers they invented the segment:offset addressing scheme and the way I understand it you're able to "group" two 16-bit registers together into a 32-bit memory address. But the same place I have also read that the CPU could only access 1MB of memory. How does that work? 2^32 equals 4,294,967,296 so I don't understand, please enlighten me :)

推荐答案

段寄存器值左移4(乘以16)并添加到偏移量"字段中.地址的一部分.

The segment register value is shifted left by 4 (multiplied by 16) and added to the "offset" part of the address address.

16 * 65536 = 1兆字节.

16 * 65536 = 1 megabyte.

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