JG82852GMSL7VP Datasheet, PDF (66/176 Pages) Intel Corporation – Intel® 852GM/852GMV Chipset Intel® 852GM/852GMV Chipset Hub (GMCH)

Register Description
R
Table 17. Attribute Bit Assignment
Bits [7, 3]
Reserved
Bits [6, 2]
Reserved
X
X
Bits [5, 1]
WE
0
X
X
0
X
X
1
X
X
1
Bits [4, 0]
RE
0
1
0
1
Description
Disabled. DDR SDRAM is disabled and all
accesses are directed to Hub Interface. The Intel
852GM/852GMV GMCH does not respond as a
Hub Interface target for any read or write access
to this area.
Read Only. Reads are forwarded to DDR
SDRAM and writes are forwarded to Hub
Interface for termination. This write protects the
corresponding DDR SDRAM segment. The Intel
852GM/852GMV GMCH will respond as a Hub
Interface target for read accesses but not for any
write accesses.
Write Only. Writes are forwarded to DDR
SDRAM and reads are forwarded to the Hub
Interface for termination. The Intel
852GM/852GMV GMCH will respond as a Hub
Interface target for write accesses but not for any
read accesses.
Read/Write. This is the normal operating mode of
main System Memory. Both read and write cycles
from the host are claimed by the Intel
852GM/852GMV GMCH and forwarded to DDR
SDRAM. The Intel 852GM/852GMV GMCH will
respond as a Hub Interface target for both read
and write accesses.
As an example, consider a BIOS that is implemented on the expansion bus. During the initialization
process, the BIOS can be shadowed in main System Memory to increase the system performance. When
BIOS is shadowed in main System Memory, it should be copied to the same address location. To
shadow the BIOS, the attributes for that address range should be set to write only. The BIOS is
shadowed by first doing a read of that address. This read is forwarded to the expansion bus. The host
then does a write of the same address, which is directed to main System Memory. After the BIOS is
shadowed, the attributes for that System Memory area are set to read only so that all writes are
forwarded to the expansion bus. Figure 3 and Table 18 show the PAM registers and the associated
attribute bits.
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Intel^® 852GM/852GMV Chipset GMCH Datasheet