VT8601 Via, VT8601 Datasheet - Page 59

• Manufacturer Part Number: VT8601
• Description: Slot-1 / Socket-370 PCI North Bridge
• Manufacturer: Via

Device 1 Offset 18 - Primary Bus Number ...................... RW
This register is read write, but internally the chip always uses
bus 0 as the primary.
Device 1 Offset 19 - Secondary Bus Number .................. RW
Note: PCI#2 must use these bits to convert Type 1 to Type 0.
Device 1 Offset 1A - Subordinate Bus Number .............. RW
Note: PCI#2 must use these bits to decide if Type 1 to Type 1
command passing is allowed.
Device 1 Offset 1C - I/O Base ........................................... RW
Device 1 Offset 1D - I/O Limit .......................................... RW
Device 1 Offset 1F-1E - Secondary Status ........................ RO
Device 1 Offset 21-20 - Memory Base .............................. RW
Device 1 Offset 23-22 - Memory Limit (Inclusive) .......... RW
Device 1 Offset 25-24 - Prefetchable Memory Base ....... RW
Device 1 Offset 27-26 - Prefetchable Memory Limit ...... RW
Revision 1.3 September 8, 1999
15-0 Reserved
15-4 Memory Base AD[31:20] .................default = 0FFFh
15-4 Memory Limit AD[31:20]........................ default = 0
15-4 Prefetchable Memory Base AD[31:20].def = 0FFFh
15-4 Prefetchable Memory Limit AD[31:20] ...................
7-0
7-0
7-0
7-4
3-0
7-4
3-0
3-0
3-0
3-0
3-0
7HFKQRORJLHV ,QF
Primary Bus Number............................... default = 0
Secondary Bus Number ........................... default = 0
Primary Bus Number............................... default = 0
I/O Base AD[15:12].......................... default = 1111b
I/O Addressing Capability....................... default = 0
I/O Limit AD[15:12] ................................ default = 0
I/O Addressing Capability....................... default = 0
Reserved
Reserved
Reserved
Reserved
:H &
:H &R R QQHFW
QQHFW
.................................. always reads 0000
........................................ always reads 0
........................................ always reads 0
........................................ always reads 0
.............................................. default = 0
........................................ always reads 0
-53-
Device 1 Offset 3F-3E – PCI-to-PCI Bridge Control ..... RW
15-4 Reserved
1-0
3
2
Device 1 Bus 0 Header Registers - PCI-to-AGP Bridge
VGA-Present on AGP
Note: VGA addresses are memory A0000-BFFFFh
and I/O addresses 3B0-3BBh, 3C0-3CFh and 3D0-
3DFh (10-bit decode).
B0000-B7FFFh and "Color" Text Mode uses B8000-
BFFFFh. Graphics modes use Axxxxh. Mono VGA
uses I/O addresses 3Bx-3Cxh and Color VGA uses
3Cx-3Dxh. If an MDA is present, a VGA will not
use the 3Bxh I/O addresses and B0000-B7FFFh
memory space;
addresses to emulate MDA modes.
Block / Forward ISA I/O Addresses
Reserved
0
1
0
1
Forward VGA accesses to PCI Bus ....... default
Forward VGA accesses to AGP Bus
Forward all I/O accesses to the AGP bus if
they are in the range defined by the I/O Base
and I/O Limit registers (device 1 offset 1C-1D)
Do not forward I/O accesses to the AGP bus
that are in the 100-3FFh address range even if
they are in the range defined by the I/O Base
and I/O Limit registers.
........................................always reads 0
.................................................... default
........................................always reads 0
VT8601 Apollo ProMedia
if not, the VGA will use those
"Mono" text mode uses