Chapter 7
Recommended BIOS Settings
225
24081D—February 2002
AMD-761™ System Controller Software/BIOS Design Guide
Preliminary Information
Registers
-----
Bits
Description
Initialized/
Required
Value
Actual
Value
Key
fcn( )
Notes
11
Dis AGP Early Probe
0b
A
1 = Disable early snoop
from AGP master running a
PCI cycle to memory
10
Dis PCI Early Probe
0b
B
1 = Disable early probe
request for write cycles
from an external PCI master
9
Dis AGP arbiter pipelining
0b
A
1 = Disable AGP arbiter from
pipelining grants onto bus
8
Southbridge lock disable
0b
B
1 = Disable flushing function
performed before granting
bus to the Southbridge
7
PM register enable
xb
P
1 = Enables R/W accesses to
PM register at 0:0x18 BAR2
– AGP Power management
6
15-Mbytes hole enable
xb
B
1 = Enable a memory hole
at 15-16 Mbytes
5
14-Mbytes hole enable
xb
B
1 = Enable a memory hole
at 14-15 MBytes
4
EV6 mode
1b
B
1 = Enable PCI decoding in
EV6 mode. Used for
opening buffers in 640K to
1-Mbyte memory address
space. Legacy USB/SCSI
devices sometimes need
this capability.
3
Target latency timer disable
1b
B
0x0x
0x84
[23]
1 = Disable AMD-751™
system controller target
latency timer on both PCI
and AGP’s PCI interfaces
2
ApcPreEn
0b
B
1 = Disables AMD-751
system controller to prefetch
data from SDRAM when a
PCI master on AGP bus reads
from main memory
1
PciPreEn
0b
B
1 = Enables AMD-751
system controller to prefetch
data from SDRAM when a
PCI master on PCI bus reads
from main memory
0
ParkPCI
0b
B
0 = PCI arbiter parks on
processor accesses to PCI
1 = Enables parking on an
external PCI master
KEY:
B= Mandatory BIOS function
A= AGP setup by BIOS
c = Calculated/set by AMD-761™ internal logic
P= Power management setup by BIOS
o = Setup by OS or OS driver
F = Performance enhancement set by BIOS
r = Hardcoded and reserved
u = PCI operational user interface
E = Elective BIOS function