Intel® 865G/865GV Chipset Datasheet - download.intel.nl - Intel

Register DescriptionAs an example, consider BIOS that is implemented on the expansion bus. During the initializationprocess, BIOS can be shadowed in main memory to increase the system performance. When BIOSis shadowed in main memory, it should be copied to the same address location. To shadow BIOS,the attributes for that address range should be set to write only. The BIOS is shadowed by firstdoing a read of that address. This read is forwarded to the expansion bus. The host then does awrite of the same address that is directed to main memory. After the BIOS is shadowed, theattributes for that memory area are set to read only so that all writes are forwarded to the expansionbus. Figure 8 and Table 7 show the PAM registers and the associated attribute bits.Figure 8. PAM Register AttributesPAM6PAM5PAM4PAM3PAM2PAM1PAM0Offset96h95h94h93h92h91h90h7 6 5 4 3 2 1 0R R WE RE R R WE REReservedReservedWrite Enable (R/W)1=Enable0=DisableRead Enable (R/W)1=Enable0=DisableRead Enable (R/W)1=Enable0=DisableWrite Enable (R/W)1=Enable0=DisableReservedReservedTable 7.PAM Register AttributesPAM Reg Attribute Bits Memory Segment Comments OffsetPAM0[3:0] Reserved 90hPAM0[7:6] Reserved 90hPAM0[5:4] R R WE RE 0F0000h–0FFFFFh BIOS Area 90hPAM1[1:0] R R WE RE 0C0000h–0C3FFFh ISA Add-on BIOS 91hPAM1[7:4] R R WE RE 0C4000h–0C7FFFh ISA Add-on BIOS 91hPAM2[1:0] R R WE RE 0C8000h–0CBFFFh ISA Add-on BIOS 92hPAM2[7:4] R R WE RE 0CC000h–0CFFFFh ISA Add-on BIOS 92hPAM3[1:0] R R WE RE 0D0000h–0D3FFFh ISA Add-on BIOS 93hPAM3[7:4] R R WE RE 0D4000h–0D7FFFh ISA Add-on BIOS 93hPAM4[1:0] R R WE RE 0D8000h–0DBFFFh ISA Add-on BIOS 94hPAM4[7:4] R R WE RE 0DC000h–0DFFFFh ISA Add-on BIOS 94hPAM5[1:0] R R WE RE 0E0000h–0E3FFFh BIOS Extension 95hPAM5[7:4] R R WE RE 0E4000h–0E7FFFh BIOS Extension 95hPAM6[1:0] R R WE RE 0E8000h–0EBFFFh BIOS Extension 96hPAM6[7:4] R R WE RE 0EC000h–0EFFFFh BIOS Extension 96h70 Intel ® 82865G/82865GV GMCH Datasheet