AMD AMD-K6-2/450 Design Guide - Page 45

Examples, base address that corresponds to 1 Gbyte 4000_0000h

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23913A/0-November 2000 Preliminary Information Embedded AMD-K6™ Processors BIOS Design Guide Examples Suppose that the range of memory from 16 Mbytes to 32 Mbytes is uncacheable, and the 8-Mbyte range of memory on top of 1 Gbyte is write-combinable. Range 0 is defined as the uncacheable range, and range 1 is defined as the writecombining range. s Extracting the 15 most-significant bits of the 32-bit physical base address that corresponds to 16 Mbytes (0100_0000h) yields a physical base address 0 field of 000_0000_1000_0000b. Because the uncacheable range size is 16 Mbytes, the physical mask value 0 field is 111_1111_1000_0000b, according to Table 16 on page 32. Bit 1 of the UWCCR register (WC0) is set to 0, and bit 0 of the UWCCR register is set to 1 (UC0). s Extracting the 15 most-significant bits of the 32-bit physical base address that corresponds to 1 Gbyte (4000_0000h) yields a physical base address 1 field of 010_0000_0000_0000b. Because the write-combining range size is 8 Mbytes, the physical mask value 1 field is 111_1111_1100_0000b, according to Table 16. Bit 33 of the UWCCR register (WC1) is set to 1 and bit 32 of the UWCCR register is set to 0 (UC1). Model 8/[F:8] Registers 33

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Model 8/[F:8] Registers
33
23913A/0—November 2000
Embedded AMD-K6™ Processors BIOS Design Guide
Preliminary Information
Examples
Suppose that the range of memory from 16 Mbytes to 32 Mbytes
is uncacheable, and the 8-Mbyte range of memory on top of 1
Gbyte is write-combinable. Range 0 is defined as the
uncacheable range, and range 1 is defined as the write-
combining range.
Extracting the 15 most-significant bits of the 32-bit physical
base address that corresponds to 16 Mbytes (0100_0000h)
yields
a
physical
base
address
0
field
of
000_0000_1000_0000b. Because the uncacheable range size
is
16
Mbytes,
the
physical
mask
value
0
field
is
111_1111_1000_0000b, according to Table 16 on page 32. Bit
1 of the UWCCR register (WC0) is set to 0, and bit 0 of the
UWCCR register is set to 1 (UC0).
Extracting the 15 most-significant bits of the 32-bit physical
base address that corresponds to 1 Gbyte (4000_0000h)
yields
a
physical
base
address
1
field
of
010_0000_0000_0000b. Because the write-combining range
size is 8 Mbytes, the physical mask value 1 field is
111_1111_1100_0000b, according to Table 16. Bit 33 of the
UWCCR register (WC1) is set to 1 and bit 32 of the UWCCR
register is set to 0 (UC1).