Intel 6 SERIES CHIPSET - DATASHEET 01-2011 Datasheet page 402

Bit
4
3
2
1
0
402
Alternate Access Mode Enable (AME) — R/W.
0 = Disabled.
1 = Alternate access read only registers can be written, and write only registers can
be read. Before entering a low power state, several registers from powered down
parts may need to be saved. In the majority of cases, this is not an issue, as
registers have read and write paths. However, several of the ISA compatible
registers are either read only or write only. To get data out of write-only
registers, and to restore data into read-only registers, the PCH implements an
alternate access mode. For a list of these registers see
Shutdown Policy Select (SPS) — R/W.
0 = PCH will drive INIT# in response to the shutdown Vendor Defined Message
(VDM). (default)
1 = PCH will treat the shutdown VDM similar to receiving a CF9h I/O write with data
value 06h, and will drive PLTRST# active.
Reserved Page Route (RPR) — R/W. Determines where to send the reserved page
registers. These addresses are sent to PCI or LPC for the purpose of generating POST
codes. The I/O addresses modified by this field are: 80h, 84h, 85h, 86h, 88h, 8Ch,
8Dh, and 8Eh.
0 = Writes will be forwarded to LPC, shadowed within the PCH, and reads will be
returned from the internal shadow
1 = Writes will be forwarded to PCI, shadowed within the PCH, and reads will be
returned from the internal shadow.
NOTE: if some writes are done to LPC/PCI to these I/O ranges, and then this bit is
flipped, such that writes will now go to the other interface, the reads will not
return what was last written. Shadowing is performed on each interface.
The aliases for these registers, at 90h, 94h, 95h, 96h, 98h, 9Ch, 9Dh, and 9Eh, are
always decoded to LPC.
Reserved
BIOS Interface Lock-Down (BILD) — R/WLO.
0 = Disabled.
1 = Prevents BUC.TS (offset 3414, bit 0) and GCS.BBS (offset 3410h, bits 11:10)
from being changed. This bit can only be written from 0 to 1 once.
Chipset Configuration Registers
Description
Section 5.13.9.
Datasheet