VT8601 Via, VT8601 Datasheet - Page 57

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

Device 0 Offset F7-F0 – BIOS Scratch Register ............. RW
Device 0 Offset F8 – DRAM Arbitration Timer 1 .......... RW
Device 0 Offset F9 – DRAM Arbitration Timer 2 .......... RW
Device 0 Offset FA – CPU Direct Access Frame Buffer
Base Address A[28:21] ...................................................... RW
Device 0 Offset FB – Frame Buffer Control ................... RW
Revision 1.3 September 8, 1999
7-0
7-4
3-0
7-4
3-0
7-0
5-4
2-0
7
6
3
7HFKQRORJLHV ,QF
No Hardware Function
AGP Timer (units of 4 DRAM Clocks)
Host Timer (units of 4 DRAM Clocks)
VGA High Priority Timer (units of 16 DRAM
Clocks)
VGA Timer (units of 16 DRAM Clocks)
A[28:21]
VGA Enable
VGA Reset ................................. (Write 1 to Reset)
Frame Buffer Size
00 None
01 2M
10 4M
11 8M
CPU Direct Access Frame Buffer
CPU Direct Access Frame Buffer Base Address
<31:29>
:H &
:H &R R QQHFW
0
1
0
1
QQHFW
Disable ...................................................default
Enable
Disable ...................................................default
Enable
.....................................................default
-51-
Device 0 Offset FC – Back Door Control 1 ..................... RW
Device 0 Offset FD – Back Door Control 2 ..................... RW
Device 0 Offset FF-FE – Back Door Device ID .............. RW
15-0 Back-Door Device ID................................ default = 0
7-2
7-3
2-0
1
0
Reserved
Back-door MAX # of AGP Request Allowed
Back-Door Device ID Enable
Reserved
Back-Door Max # of AGP Requests the Device can
Handle
000 1-Request ............................................... default
001 2-Requests
111 8-Requests
… …
0
1
0
1
Read RXA7 will return 7 ....................... default
Read RxXA7 will have number programmed at
RxFD
Use Rx3-2’s value for Rx3-2 read ......... default
Use the value in RxFE-FF
........................................always reads 0
Device 0 Bus 0 Host Bridge Registers
VT8601 Apollo ProMedia