82830MP Datasheet, PDF (60/159 Pages) Intel Corporation – Intel 830MP Chipset: 82830MP Graphics and Memory Controller Hub (GMCH-M)

Intel® 830MP Chipset
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As an example, consider a BIOS that is implemented on the expansion bus. During the initialization
process, the BIOS can be shadowed in main memory to increase the system performance. When BIOS is
shadowed in main 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 memory. After the BIOS is shadowed, the attributes for that memory
area are set to read only so that all writes are forwarded to the expansion bus. Figure 8 and Table 21
show the PAM registers and the associated attribute bits:
Figure 8. PAM Registers
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Datasheet
298338-001