82830MP Datasheet, PDF (93/159 Pages) Intel Corporation – Intel 830MP Chipset: 82830MP Graphics and Memory Controller Hub (GMCH-M)

Intel^® 830MP Chipset
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4.5.2.17
MBASE - Memory Base Address Register - Device #1
Address Offset:
Default Value:
Access:
Size:
20-21h
FFF0h
Read/Write
16 bits
This register controls the CPU to PCI1 non-prefetchable memory access routing based on the following
formula:
MEMORY_BASE=< address =<MEMORY_LIMIT
The upper 12 bits of the register are read/write and correspond to the upper 12 address bits A[31:20] of
the 32-bit address. The bottom 4 bits of this register are read-only and return zeroes when read. The
configuration software must initialize this register. For the purpose of address decode, address bits
A[19:0] are assumed to be 0. Thus, the bottom of the defined memory address range will be aligned to a
1-MB boundary.
Bit
15: 4
3:0
Description
Memory Address Base (MEM_BASE). Corresponds to A[31:20] of the memory address.
Default Value=000000000000.
Reserved.
4.5.2.18
MLIMIT - Memory Limit Address Register - Device #1
Address Offset:
Default Value:
Access:
Size:
22-23h
0000h
Read/Write
16 bits
This register controls the CPU to PCI1 non-prefetchable memory access routing based on the following
formula:
MEMORY_BASE=< address =<MEMORY_LIMIT
The upper 12 bits of the register are read/write and correspond to the upper 12 address bits A[31:20] of
the 32-bit address. The bottom 4 bits of this register are read-only and return zeroes when read. The
configuration software must initialize this register. For the purpose of address decode, address bits
A[19:0] are assumed to be FFFFFh. Thus, the top of the defined memory address range will be at the top
of a 1-MB aligned memory block.
Bit
15: 4
3:0
Description
Memory Address Limit (MEM_LIMIT). Corresponds to A[31:20] of the memory address.
Default Value=000000000000.
Reserved.
Note: Memory range covered by MBASE and MLIMIT registers are used to map non-prefetchable PCI1/AGP
address ranges (typically where control/status memory-mapped I/O data structures of the graphics
298338-001
Datasheet
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