4
Overview
Chapter 1
AMD-761™ System Controller Software/BIOS Design Guide
24081D—February 2002
Preliminary Information
The AMD-761 system controller provides BIOS the ability to
override the reporting of fast write and 4X rate support. This
override function is accomplished through a write to a separate
register, which is required because the AGP Status register is
specified as read-only in the AGP specification.
R e f e r t o S e c t i o n 6 . 2 o n p a g e 2 0 8 fo r d e t a i l s o f t h i s
implementation.
Interrupt Pin Control
R/W Attributes
The Int_Pin field in the AGP/PCI Interrupt and Bridge Control
register (Dev 1:F0:0x3C) is read-only by default and initializes
to all 0s. If the BIOS is required to initialize this field to
another value, it must first change this field to R/W by setting
the Int_Pin_Cntl bit in the Miscellaneous Device 1 Control
register (Dev 1:F0:0x40).
The AMD-761 system controller does not use the Int_Pin field
internally, the register is provided for software compatibility only.
Silicon Revisions
The reader is advised to read the
AMD-761™ System Controller
Revision Guide
, order# 23613, for the most current information
for the version of silicon being used. The silicon revision is
available by reading the PCI revision ID and Class Code
register in Dev 0:F0:0x08.
1.1.3
Power-On Reset Initialization
All of the AMD-761 system controller’s configuration registers
must be initialized by BIOS after initial power-on, paying especially
close attention to the registers that are not initialized to a known
value.
T h e A M D -7 6 1 s y s t e m c o n t r o l l e r i s r e s e t w h e n t h e
Southbridge’s PCIRST# pin is asserted, which occurs when
transitioning from the Mechanical Off, S5, S4, or S3 sleep
states.
To accommodate support of the Advanced Configuration and
Powe r I n t e r f a c e ( AC P I ) S 3 ( s u s p e n d t o R A M ) p owe r
management state, the registers listed in Table 1 on page 5 are
not initialized to a known state after reset (RESET# asserted),
and they must be initialized by BIOS after initial power-on for
proper operation. These registers retain the value programmed
by BIOS after subsequent assertions of the RESET# pin when
transitioning to and from the S3 sleep state.