AMD 8151 Bits, Description, GARTHI GART base address register high, Link Command Register

24888 Rev 3.03 - July 12, 2004AMD-8151TMAGP Tunnel Data Sheet

11:0	APSIZE: graphic virtual memory aperture size. Read-write (except bits[11, 7:6, and 2:0] which
	are read only, fixed at the default value). This field specifies the size of the aperture pointed to by
	DevA:0x10. This field also controls read only versus read-write control over several bits in
	DevA:0x10. It is encoded as follows:
								DevA:0x10	DevA:0x10
	Bits[10,	9,	8, 5,		4,	3]	Aperture size	read-write bits	read-only bits
	1	1	1	1	1	1	32 MB	[63:25]	[24:0]
	1	1	1	1	1	0	64 MB	[63:26]	[25:0]
	1	1	1	1	0	0	128 MB	[63:27]	[26:0]
	1	1	1	0	0	0	256 MB	[63:28]	[27:0]
	1	1	0	0	0	0	512 MB	[63:29]	[28:0]
	1	0	0	0	0	0	1024 MB	[63:30]	[29:0]
	0	0	0	0	0	0	2048 MB	[63:31]	[30:0]
	It is expected that the state of this field is copied into the host by software. Note: DevA:0x10[2] is
	“read; write once,” even though it is shown as read-only above. Also, based on the state of
	DevA:0x10[2], DevA:0x10[63:32] may be read-only, all zeros.
AGP Device GART Pointer									DevA:0xB8

This register controls no hardware in the IC. It is expected that the state of this register is copied into the host by software.

Default: 0000 0000 0000 0000h		Attribute: Read-write.
Bits	Description
63:32	GARTHI: GART base address register high.
31:12	GARTLO: GART base address register low.
11:0	Reserved.
Link Command Register		DevA:0xC0
Default: 0060 0008h		Attribute: See below.
Bits	Description
31:29	Slave/primary interface type. Read only.

28DOUI: drop on uninitialized link. Read-write. This specifies the behavior of transactions that are sent to uninitialized links. 0=Transactions that are received by the IC and forwarded to a side of the tunnel, when DevA:0x[C4/C8][INITCPLT and ENDOCH] for that side of the tunnel are both low, remain in buffers awaiting transmission indefinitely (waiting for INITCPLT to be set high). 1=Trans- actions that are received by the IC and forwarded to a side of the tunnel, when DevA:0x[C4/C8][INITCPLT and ENDOCH] for that side of the tunnel are both low, behave as if ENDOCH were high. Note: this bit is cleared by PWROK reset but not by RESET#.

27DEFDIR: default direction. Read-write. 0=Send AGP master requests to the master link host as specified by DevA:0xC0[MASHST]. 1=Send AGP master requests to the opposite side of the tunnel.

24