如何開啟A20位址線 ?

 

Assembly code

In al, 0x92

Or al, 2

Out 0x92, al

 

Another way is to use the BIOS.

INT 15, 2401

mov ax, 0x2401

int 0x15

Legacy BIOS V.S. UEFI BIOS

	Legacy BIOS	UEFI BIOS
Language	Interrupt	C (99%)
Resource	Interrupt Hardcode Memory Access Hardcode I/O Access	Driver \ Protocols
Processor	X86 16-bits	CPU Protected Mode (Flat Mode)
Target	Binary Code	Removable Binary Drivers
Expand	Hook Interrupt	Load Driver
OS Bridge	ACPI	Run Time Driver Service
3rd Party ISV & IHV	Bad for Support	Easy for Support and Multi-Platforms

如何切換80 port Debug燈號 -> LPC or PCI ?

platform : Intel ICH8

在ICH8 Datasheet可以找到相關資訊

GCS = RCBA (Root Complex Base Address) + 3410h

Bit 2 : 設為 1 為輸出給 PCI 上的 80 port debug card

Bit 2 : 設為 0 為輸出給 LPC 上的 80 port debug card

 

RCBA 可以從 Device 31 : Function 0 取得