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11-40 Vol. 3
MEMORY CACHE CONTROL
IA32_MTRR_PHYSBASE5 = 0000 0000 A000 0001H
IA32_MTRR_PHYSMASK5 = 0000 000F FF80 0800H
Caches A0000000-A0800000 as WC type.
This MTRR setup uses the ability to overlap any two memory ranges (as long as the
ranges are mapped to WB and UC memory types) to minimize the number of MTRR
registers that are required to configure the memory environment. This setup also
fulfills the requirement that two register pairs are left for operating system usage.
11.11.3.1 Base and Mask Calculations for Greater-Than 36-bit Physical
Address Support
For Intel 64 and IA-32 processors that support greater than 36 bits of physical
address size, software should query CPUID.80000008H to determine the maximum
physical address. See the example.
Example 11-3. Setting-Up Memory for a System with a 40-Bit Address Size
If a processor supports 40-bits of physical address size, then the PhysMask field (in
IA32_MTRR_PHYSMASKn registers) is 28 bits instead of 24 bits. For this situation,
Example 11-2 should be modified as follows:
IA32_MTRR_PHYSBASE0 = 0000 0000 0000 0006H
IA32_MTRR_PHYSMASK0 = 0000 00FF FC00 0800H
Caches 0-64 MByte as WB cache type.
IA32_MTRR_PHYSBASE1 = 0000 0000 0400 0006H
IA32_MTRR_PHYSMASK1 = 0000 00FF FE00 0800H
Caches 64-96 MByte as WB cache type.
IA32_MTRR_PHYSBASE2 = 0000 0000 0600 0006H
IA32_MTRR_PHYSMASK2 = 0000 00FF FFC0 0800H
Caches 96-100 MByte as WB cache type.
IA32_MTRR_PHYSBASE3 = 0000 0000 0400 0000H
IA32_MTRR_PHYSMASK3 = 0000 00FF FFC0 0800H
Caches 64-68 MByte as UC cache type.
IA32_MTRR_PHYSBASE4 = 0000 0000 00F0 0000H
IA32_MTRR_PHYSMASK4 = 0000 00FF FFF0 0800H
Caches 15-16 MByte as UC cache type.
IA32_MTRR_PHYSBASE5 = 0000 0000 A000 0001H
IA32_MTRR_PHYSMASK5 = 0000 00FF FF80 0800H
Caches A0000000-A0800000 as WC type.