how does the OS know the real size of the physical memory?

Asked 2012-04-26T16:07:23.157

When the OS is loaded at the moment the computer is started, how does the OS know the hardware information, is there some io instruction or the booter program get information from the bios.??

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An OS that boot from a BIOS-based system query the Query System Address Map function using INT 0x15, AX=0xE820.

A UEFI-based OS would typically get the physical memory map using the GetMemoryMap() interface.

answered 2012-07-25T19:37:53.617

how does the OS know the real size of the physical memory?

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