Intel S975XBX2 Product Specification - Page 47
Technical Reference
UPC - 735858186506
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2 Technical Reference What This Chapter Contains 2.1 Memory Resources 47 2.2 DMA Channels 49 2.3 Fixed I/O Map 50 2.4 PCI Configuration Space Map 51 2.5 Interrupts 52 2.6 PCI Conventional Interrupt Routing Map 53 2.7 Connectors 54 2.8 Jumper Block 67 2.9 Mechanical Considerations 68 2.10 Electrical Considerations 70 2.11 Thermal Considerations 72 2.12 Reliability 74 2.13 Environmental 75 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 (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 14 shows a schematic of 47