从给定的物理地址和有效地址中查找段地址 [英] Find Segment address from given physical and effective address

问题描述

如何从给定数据中找到段地址?

物理地址 = 0x119B，有效地址 = 0x10AB

公式是什么?

解决方案

x86 16 位实模式中的有效地址只是 20 位 segment:offset 地址.给你的问题是确定一个段值，当与有效地址 0x10AB 结合产生一个物理(线性)地址 0x119B 时.

物理地址可以从 segment:offset 对使用公式 physaddr=(segment<<4)+offset 或 physaddr=(段*0x10)+偏移量.稍微修改一下公式:

<块引用>

physaddr = (segment*0x10)+offsetphysaddr-offset = 段*0x10(physaddr-offset)/0x10 = 段段 = (physaddr-offset)/0x10

既然我们知道段的公式是segment = (physaddr-offset)/0x10，我们可以执行计算来找到您问题的答案:

<块引用>

segment = (0x119B-0x10AB)/0x10段 = 0xF0/0x10段 = 0xF

我们可以通过将它代入物理地址的原始方程来检查这个结果并得到:

<块引用>

physaddr = (0xF*0x10)+0x10AB = 0x119B.

how to find a segment address from given data?

Physical address = 0x119B, Effective address = 0x10AB

what could be the formula?

解决方案

The effective address in x86 16-bit real mode is just the offset portion of a 20-bit segment:offset address. The question you have been given is to determine a segment value when combined with the effective address 0x10AB yields a physical (linear) address of 0x119B.

The physical address can be computed from a segment:offset pair with the formula physaddr=(segment<<4)+offset or physaddr=(segment*0x10)+offset. Reworking the formula a bit:

physaddr = (segment*0x10)+offset
physaddr-offset = segment*0x10
(physaddr-offset)/0x10 = segment
segment = (physaddr-offset)/0x10

Now that we know the formula for segment is segment = (physaddr-offset)/0x10 we can perform the calculation to find the answer for your question:

segment = (0x119B-0x10AB)/0x10
segment = 0xF0/0x10
segment = 0xF

We can check this result by plugging it into the original equation for physical address and get:

physaddr = (0xF*0x10)+0x10AB = 0x119B.

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