Specifications

 2012 Advanced Micro Devices, Inc.
ACPI/SMBUS Controller (bus-0, dev-20, fun-0)
AMD SP5100 Register Programming Requirements
Page 18
2.17 Legacy DMA Prefetch Enhancement
ASIC Rev Register Settings Function/Comment
All Revs SP5100 Smbus_PCI_config 0x43 [0] = 1 (only when
the system is non-DOS mode)
Enables legacy DMA prefetch enhancement for channel 0,
1, 2, and 3. This bit should be set to improve DMA out (eg
memory-to-floppy disk) performance.
Note: This bit should only be enabled in the ACPI method
(called by the OS). This ensures that it is enabled only
when the system is in Window mode. Under DOS mode,
this feature may not work properly and may cause the
floppy to malfunction.
Smbus_PCI_config 0x41 [7] = 1
Lpc_PCI_config 0x78 [0] = 0
Set these bits to make LPC DMA work properly.
SATA
USB
SMBUS
PATA
AC97
HD AUDIO
LPC
PCI
For register details refer to
the sections check-marked
in the SP5100 Register
Reference Guide
X
RTC
ACPI
PM REG
A-LINK
I/O REG
XIOAPIC
2.18 USB Set BM_STS
ASIC Rev Register Settings Function/Comment
All Revs SP5100 PM_IO 0x66 [6] = 0
For balanced power saving and USB performance, allow
USB DMA to cause pop-up. Other register settings for C
state should be followed for the system to work properly.
Note: Refer to USB register settings section for the corresponding USB register settings that are required to be
programmed when the above registers are programmed. For the AMD platform, PM_IO 0x66 [6], and register settings in
the USB register settings section should be programmed.
SATA
USB
SMBUS
PATA
AC97
HD AUDIO
LPC
PCI
For register details refer to
the sections check-marked
in the SP5100 Register
Reference Guide
RTC
ACPI
PM REG
A-LINK
I/O REG
XIOAPIC
x
2.19 Enabling Spread Spectrum
ASIC Rev Register Settings Function/Comment
All Revs SP5100 PM_IO 0x42 [7] = 1
Enables spread spectrum on PCI clocks with -0.5%
spread. In external clock mode, the internal SS when
enabled will down spread the PCI clocks. The 100 MHz
PCIe

clock SB_SRC from the external clock generator
should not have spread spectrum enabled if the internal
spread is enabled. Refer to PA_SP5100AGx for more
information on enabling the spread spectrum.
SATA
USB
SMBUS
PATA
AC97
HD AUDIO
LPC
PCI
For register details refer to
the sections check-marked
in the SP5100 Register
Reference Guide
RTC
ACPI
PM REG
A-LINK
I/O REG
XIOAPIC
x