Intel DESKTOP BOARD D955XBK - Technical Reference; Memory Resources

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2 Technical Reference
What This Chapter Contains
2.1 Memory Resources......................................................................................................45
2.2 DMA Channels.............................................................................................................47
2.3 Fixed I/O Map...............................................................................................................48
2.4 PCI Configuration Space Map......................................................................................49
2.5 Interrupts......................................................................................................................50
2.6 PCI Conventional Interrupt Routing Map .....................................................................51
2.7 Connectors...................................................................................................................53
2.8 Jumper Block ...............................................................................................................67
2.9 Mechanical Considerations..........................................................................................68
2.10 Electrical Considerations..............................................................................................71
2.11 Thermal Considerations...............................................................................................73
2.12 Reliability......................................................................................................................75
2.13 Environmental ..............................................................................................................76
2.14 Regulatory Compliance................................................................................................77
2.1 Memory Resources
2.1.1 Addressable Memory
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 (firmware
hub), 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/firmware hub (2 MB)
• 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.