24888 Rev 3.03 - July 12, 2004 AMD-8151
TM
AGP Tunnel Data Sheet
24
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.
Link Command Register DevA:0xC0
Default: 0060 0008h Attribute: See below.
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.
Bits Description
63:32 GARTHI: GART base address register high.
31:12 GARTLO: GART base address register low.
11:0 Reserved.
Bits Description
31:29 Slave/primary interface type. Read only.
28 DOUI: 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#.
27 DEFDIR: 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.
