在实模式下访问4GB RAM [英] accessing 4GB RAM in real mode

问题描述

是否可以通过启用A20在实模式下使用4GB内存，而无需切换到保护模式，也不会丢失BIOS中断?

Is it possible to using 4GB ram in real mode through enabling A20, without switching to protect mode, and without loosing BIOS interrupts?

推荐答案

您可以通过使用虚幻模式来实现.此模式使用一个限制为4 GB的选择器加载一个或多个段寄存器.此模式有两种形式，大虚幻模式和巨大虚幻模式.前者允许访问1 MB以上的数据，后者允许访问1 MB以上的代码和数据.但是，由于实模式中断仅保留EIP的低16位，因此很难设置巨大的虚幻模式.有关更多信息，请参见此页面.

You can do this by using Unreal Mode. This mode loads one or more of the segment registers with a selector that has a limit of 4 GB. There are two forms of this mode, Big Unreal Mode and Huge Unreal Mode. The former allows accessing data above 1 MB, and the latter allows code and data above 1 MB. Huge Unreal Mode is difficult to set up, though, because real mode interrupts only preserve the low 16 bits of EIP. See this page for more information.

如果可能，您还可能希望从BIOS获取内存映射，因为某些内存已映射到某些硬件，因此不能用作普通内存.有关更多信息，请参见此页面.

You also may want to get a memory map from the BIOS if possible, since some memory is memory mapped to certain hardware, and cannot be used as normal memory. See this page for more information.

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