Tseg; Pre-Allocated Memory; Pci Memory Address Range (Tolud - 4 Gb); Table 9-4. Pre-Allocated Memory Example For 64-Mb Dram And 1-Mb Tseg - Intel 925 - Pentium D 925 3.0GHz 800MHz 4MB-Cache Socket 775 CPU Datasheet

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9.2.2

TSEG

TSEG is optionally 1 MB, 2 MB, or 8 MB in size. SMM-mode processor accesses to enabled
TSEG access the physical DRAM at the same address. Non-processor originated accesses are not
allowed to SMM space. PCI Express and DMI originated cycles to enabled SMM space are
handled as invalid cycle type with reads and writes to location 0 and byte enables turned off for
writes. When the extended SMRAM space is enabled, processor accesses to the TSEG range
without SMM attribute or without WB attribute are also forwarded to memory as invalid accesses.
Non-SMM-mode write-back cycles that target TSEG space are completed to main memory for
cache coherency. When SMM is enabled, the maximum amount of memory available to the
system is equal to the amount of physical main memory minus the value in the TSEG register
which is fixed at 1 MB, 2 MB, or 8 MB.
9.2.3

Pre-allocated Memory

Voids of physical addresses that are not accessible as general system memory and reside within
system memory address range (< TOLUD) are created for SMM-mode and legacy VGA graphics
compatibility. It is the responsibility of BIOS to properly initialize these regions. Table 9-4
details the location and attributes of the regions.

Table 9-4. Pre-Allocated Memory Example for 64-MB DRAM and 1-MB TSEG

Memory Segments
0000_0000h – 03DF_FFFFh
03E0_0000h – 03EF_FFFFh
03F0_0000h – 03FF_FFFFh
9.3 PCI Memory Address Range (TOLUD – 4 GB)
This address range, from the top of physical memory to 4 GB (top of addressable memory space
supported by the MCH) is normally mapped via the DMI to PCI.
Note: AGIP Aperture no longer exists with PCI Express.
®
Intel 82925X/82925XE MCH Datasheet
Attributes
R/W Available system memory 62 MB
SMM Mode Only - TSEG Address Range and Pre-allocated
processor reads memory
R/W Pre-allocated Graphics VGA memory.
System Address Map
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