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AMD-761™ System Controller Programmer’s Interface
Chapter 2
AMD-761™ System Controller Software/BIOS Design Guide
24081D—February 2002
Preliminary Information
Programming Notes
If the target latency bit is set (bit 23 of Dev 0:F0:0x84), then the delayed transactions enable (bit 2) must be set when the
front-side bus is clocked at 66 MHz.
When enabling PCI ordering rules compliance, it is recommended that delayed transactions be enabled simultaneously
for optimal performance.
Refer to See Chapter 5, “PCI Bus Interface” on page 195 for more information on the transaction options in the AMD-761
system controller. Refer to See Chapter 7, “Recommended BIOS Settings” on page 211 for the recommended bit settings
for these bits.
Note that the WSC_DIR pin is implemented only in silicon revisions B4 and above and must be treated as Reserved (write
a 0) in all other silicon revisions.
Bit Definitions
PCI Control (Dev0:F0:0x4C)
Bit
Name
Function
31—4
Reserved
Reserved
3
WSC_DIR
Write Snoop Complete Direction Control
This bit controls the direction and function of the Write Snoop Complete (WSC#) pin.
Refer to the
AMD-761™ System Controller Datasheet
, order# 24088, for a full description
of the WSC# pin.
0 = Bidirectional mode for use with Southbridges that drive WSC# as an output
and
sample WSC# as an input (such as the AMD-766™ peripheral bus controller). In this
mode, the WSC# pin of the AMD-761 system controller defaults as an input and is
driven by the Northbridge only after the pin is first asserted by the Southbridge.
1 = Unidirectional mode for use with Southbridges that only sample WSC# as an input.
In this mode, the WSC# pin is always driven by the AMD-761 system controller.
Note:
This bit is implemented only in silicon revision B4 and above. It is reserved in all
previous silicon revisions and must be cleared.
2
PCI_DT_En
Delayed Transactions Enable (PCI)
0 = Delayed transactions disabled on the PCI interface
1 = Delayed transactions enabled on the PCI interface
1
PCI_OR_En
Ordering Rules Compliance Enable (PCI)
This bit controls how the AMD-761 system controller PCI bus interface orders transactions.
0 = PCI ordering rules compliance disabled
1 = PCI ordering rules compliance enabled
0
Func1_En
Function 1 Enable
This bit controls access to device 0, function 1 configuration space (DDR PDL registers).
Refer to “Device 0, Function 1: DDR PDL Configuration Registers” on page 97 for more
information on the function 1 registers.
0 = Device 0, function 1 disabled
1 = Device 0, function 1 enabled