AMD SB600 Specifications download pdf (Page 44)

2008 Advanced Micro Devices Inc.

High Precision Event Timer (HPET)

AMD SB600 BIOS Developer’s Guide (Public Version) Proprietary

Page 44

12 High Precision Event Timer (HPET)

The SB600 includes an industry standard High Precision Event Timers (HPET). The details and the

operation of the timer are described in the IA-PC HPET specification. This section describes the timer

initialization in the SB600 chipset.

12.1 Initialization

For SB600 is HPET usage is required, then during the early POST, the timer base address must be

programmed in Device 14h, Function 0, register 14h. This base address is also reported to the operating

system through the ACPI table as specified in the specification. In addition, the HPET interrupts may also

be enabled through Device 14h, Function 0, register 64h, bit 10.

12.1.1 Sample Initialization Code

HpetBaseAddress EQU 0FED00000H ; OEM specific address

; Set Base address in Device 14h, Function 0, Register 14h

mov dx,0CF8h ; PCI index register

mov eax,8000A014h ; Bus 0, Device 14h, Function 0, Register 14h

out dx,eax ; Set PCI index to register 14h

mov dx,0CFCh ; PCI data register

mov eax,0FED00000h ; Base address, OEM specific

out dx,eax

; Enable the HPET interrupts, if needed. Set Device 14h, Function 0, Register 64h, bit 10

mov dx,0CF8h ; PCI index register

mov eax,8000A064h ; Bus 0, Device 14h, Function 0, Register 64h

out dx,eax ; Set PCI index to register 64h

mov dx,0CFCh ; PCI data register

in eax,dx ; Read current value of register 64h

or eax,00000400h ; Set bit 10

out dx,eax

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AMD SB600 Specifications Page 44