Intel BB5520UR Product Specification - Page 46
Publishing System Memory, Memory Interleaving
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Functional Architecture Intel® Server Boards S5520HC, S5500HCV, and S5520HCT TPS 3.3.4 z z z z Publishing System Memory The BIOS displays the "Total Memory" of the system during POST if the "Quiet Boot" is disabled in the BIOS Setup. This is the total size of memory discovered by the BIOS during POST, and is the sum of the individual sizes of installed DDR3 DIMMs in the system. The BIOS also provides the total memory of the system in the BIOS setup (Main page and Advanced | Memory Configuration Page). This total is the same as the amount described by the previous bullet. The BIOS displays the "Effective Memory" of the system in the BIOS Setup (Advanced | Memory Configuration Page). The term Effective Memory refers to the total size of all active DDR3 DIMMs (not disabled) and not being used as redundant units in Mirrored Channel Mode. If Quiet Boot is disabled, the BIOS displays the total system memory on the diagnostic screen at the end of POST. This total is the same as the amount described by the first bullet. 3.3.4.1 Memory Reservation for Memory-mapped Functions A region of size of 40 MB of memory below 4 GB is always reserved for mapping chipset, processor, and BIOS (flash) spaces as memory-mapped I/O regions. This region appears as a loss of memory to the operating system. This (and other) reserved regions are reclaimed by the operating system if PAE is enabled in the operating system. In addition to this memory reservation, the BIOS creates another reserved region for memorymapped PCI Express* functions, including a standard 64 MB or 256 MB of standard PCI Express* MMIO configuration space. This is based on the setup selection, "Maximize Memory below 4GB". If this is set to "Enabled", the BIOS maximizes usage of memory below 4 GB, for an operating system without PAE capability, by limiting PCI Express* Extended Configuration Space to 64 buses, rather than the standard 256 buses. 3.3.4.2 High-Memory Reclaim When 4 GB or more of physical memory is installed (physical memory is the memory installed as DDR3 DIMMs), the reserved memory is lost. However, the Intel® 5500/5520 I/O Hub provides a feature called high-memory reclaim, which allows the BIOS and the operating system to remap the lost physical memory into system memory above 4 GB (the system memory is the memory the processor can see). The BIOS always enables high-memory reclaim if it discovers installed physical memory equal to or greater than 4 GB. For the operating system, you can recover the reclaimed memory only if the PAE feature in the processor is supported and enabled. Most operating systems support this feature. For details, see your operating system's relevant manuals. 3.3.5 Memory Interleaving The Intel® Xeon® Processor 5500 Series supports the following memory interleaving mode: 32 Revision 1.8 Intel order number E39529-013
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