Intel Desktop Board D975XBX BOXD975XBXLKR ユーザーズマニュアル

 

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The board utilizes 8 GB of addressable system memory.  Typically the address space that is 
allocated for PCI Conventional bus add-in cards, PCI Express configuration space, BIOS (SPI 
Flash device), and chipset overhead resides above the top of DRAM (total system memory).  On a 
system that has 8 GB of system memory installed, it is not possible to use all of the installed 
memory due to system address space being allocated for other system critical functions.  These 
functions include the following: 
•  BIOS/SPI Flash device (8 Mbit) 
•  Local APIC (19 MB) 
•  Digital Media Interface (40 MB) 
•  Front side bus interrupts (17 MB) 
•  PCI Express configuration space (256 MB) 
•  MCH base address registers, internal graphics ranges, PCI Express ports (up to 512 MB) 
•  Memory-mapped I/O that is dynamically allocated for PCI Conventional and PCI Express  

add-in cards 

The board provides the capability to reclaim the physical memory overlapped by the memory 
mapped I/O logical address space.  The board remaps physical memory from the top of usable 
DRAM boundary to the 4 GB boundary to an equivalent sized logical address range located just 
above the 4 GB boundary.  Figure 16 shows a schematic of the system memory map.  All installed 
system memory can be used when there is no overlap of system addresses.