AMD 8151 specifications Configuration spaces, Memory mapped address spaces, Register attributes

24888 Rev 3.03 - July 12, 2004			AMD-8151TMAGP Tunnel Data Sheet
The following are configuration spaces:
Device	Function	Mnemonic	Registers
"A"	0	DevA:0xXX	AGP device header; link and AGP capabilities blocks
"B"	0	DevB:0xXX	PCI-PCI bridge registers for AGP

Table 3: Configuration spaces.

The IC does not claim configuration-register accesses to unimplemented functions within its devices (they are forwarded to the other side of the tunnel). Accesses to unimplemented register locations within implemented functions are claimed; such writes are ignored and reads always respond with all zeros.

The following are memory mapped spaces:

Base address	Size	Mnemonic	Registers
register	(bytes)
DevA:0x10	Variable	None	Graphic virtual memory aperture; minimum of 32 megabytes.
DevA:0xB8	4K	None	GART block in physical memory.

Table 4: Memory mapped address spaces.

The following are register attributes found in the register descriptions.

Type	Description
Read or read-only	Capable of being read by software. Read-only implies that the register cannot be written to by
	software.
Write	Capable of being written by software.
Set by hardware	Register bit is set high by hardware.
Write once	After RESET#, these registers may be written to once. After being written, they become read only
	until the next RESET# assertion. The write-once control is byte based. So, for example, software
	may write each byte of a write-once DWORD as four individual transactions. As each byte is
	written, that byte becomes read only.
Write 1 to clear	Software must write a 1 to the bit in order to clear it. Writing a 0 to these bits has no effect.
Write 1 only	Software can set the bit high by writing a 1 to it. However subsequent writes of 0 will have no
	effect. RESET# must be asserted in order to clear the bit.

Table 5: Register attributes.

5.2AGP Device Configuration Registers

These registers are located in PCI configuration space, in the first device (device A), function 0. See section 5.1.2 for a description of the register naming convention.

AGP Vendor And Device ID Register		DevA:0x00
Default: 7454 1022h		Attribute: Read only.
Bits	Description
31:16	AGP device ID.
15:0	Vendor ID.

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