JG82855GMESL7VN Datasheet, PDF (71/213 Pages) Intel Corporation – Intel® 855GM/855GME Chipset Graphics and Memory Controller Hub (GMCH)

Register Description
R
Table 26. PAM Registers and Associated System Memory Segments
PAM Reg
PAM0[3:0]
PAM0[7:4]
PAM1[3:0]
PAM1[7:4]
PAM2[3:0]
PAM2[7:4]
PAM3[3:0]
PAM3[7:4]
PAM4[3:0]
PAM4[7:4]
PAM5[3:0]
PAM5[7:4]
PAM6[3:0]
PAM6[7:4]
Attribute Bits
System Memory Segment
Reserved
R
R
WE RE
0F0000h–0FFFFFh
R
R
WE RE
0C0000h–0C3FFFh
R
R
WE RE
0C4000h–0C7FFFh
R
R
WE RE
0C8000h–0CBFFFh
R
R
WE RE
0CC000h–0CFFFFh
R
R
WE RE
0D0000h–0D3FFFh
R
R
WE RE
0D4000h–0D7FFFh
R
R
WE RE
0D8000h–0DBFFFh
R
R
WE RE
0DC000h–0DFFFFh
R
R
WE RE
0E0000h–0E3FFFh
R
R
WE RE
0E4000h–0E7FFFh
R
R
WE RE
0E8000h–0EBFFFh
R
R
WE RE
0EC000h–0EFFFFh
Comments
Offset
59h
BIOS Area
59h
ISA Add-on BIOS 5Ah
ISA Add-on BIOS 5Ah
ISA Add-on BIOS 5Bh
ISA Add-on BIOS 5Bh
ISA Add-on BIOS 5Ch
ISA Add-on BIOS 5Ch
ISA Add-on BIOS 5Dh
ISA Add-on BIOS 5Dh
BIOS Extension 5Eh
BIOS Extension 5Eh
BIOS Extension 5Fh
BIOS Extension 5Fh
For details on overall system address mapping scheme see the Address Decoding section of this
document.
DOS Application Area (00000h–9FFFh)
The DOS area is 640 kB in size and it is further divided into two parts. The 512-kB area at 0 to
7FFFFh is always mapped to the main system memory controlled by the GMCH, while the 128-
kB address range from 080000 to 09FFFFh can be mapped to PCI0 or to main DDR SDRAM. By
default this range is mapped to main system memory and can be declared as a main system
memory hole (accesses forwarded to PCI0) via GMCH’s FDHC Configuration register.
Video Buffer Area (A0000h–BFFFFh)
Attribute Bits do not control this 128-kB area. The Host-initiated cycles in this region are always
forwarded to either PCI0 or PCI2 unless this range is accessed in SMM mode. Routing of
accesses is controlled by the Legacy VGA Control Mechanism of the “Virtual” PCI-PCI Bridge
Device embedded within the GMCH.
This area can be programmed as SMM area via the SMRAM register. When used as an SMM
space, this range can not be accessed from the Hub interface.
Expansion Area (C0000h–DFFFFh)
This 128-kB area is divided into eight 16-kB segments that can be assigned with different
attributes via PAM Control register as defined in Figure 5 and Table 26.
Datasheet
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