Specifications

© 2008 Advanced Micro Devices Inc.
A-Link Bridge
AMD SB600 BIOS Developer’s Guide (Public Version) Proprietary
Page 41
11 A-Link Bridge
11.1 A-Link Registers
The registers are accessed using an address-register/data-register mechanism. The address register
is AB_INDX[31:0], and the data register is AB_DATA[31:0].
31:30 29:17 16:2 1:0
RegSpace[1:0] Reserved Register address[16:2] Reserved
AB_INDX [31:0]
31:0
Data[31:0]
AB_DATA[31:0]
RegSpace[1:0]
00b AXINDC Index/Data Registers. (AX_INDXC)
01b AXINPD Index/Data Registers (AX_INDXP)
10b A-Link Express Configuration (AXCFG)
11b A-Link Bridge Configuration (ABCFG)
Definition of RegSpace[1:0]
In order to read or write a particular register, the software will write the register address and the
register space identifier to AB_INDX and then do a read or write to AB_DATA. This is
analogous to how PCI configuration reads and writes work through I/O addresses CF8h/CFCh.
The location of AB_INDX in the I/O space is defined by the abRegBaseAddr register located at
Device 14h, function 0, register 0F0h. The AB_DATA register address is offset 4h from the
AB_INDX address. The address of the AB_INDX must be 8 byte aligned.
31:3 2:0
BaseAddr[31:3] Rsv
abRegBAR[31:0] at Bus 0, Device 14h, Function 0, Register 0F0h
AXCFG and ABCFG registers are accessed indirectly through AB_INDX/AB_DATA. To read or
write a particular register through AB_INDX/AB_DATA, the register address and the register
space identifier is first written to AB_INDX. The specified register is then accessed by doing a
read or write to AB_DATA (see the example below).
Access to AXINDC and AXINDP registers requires a second level of indirection. Registers in
these spaces are addressed through the following indirection registers:
AX_INDEXC/AX_DATAC and AX_INDEXP/AX_DATAP.