When 4 GB or more of memory is installed, why does Windows report less memory than is actually installed?
With Windows Server versions that use 32-bit addressing on PC/Intel® (x86) architecture, most PCI devices can’t have their address spaces mapped above the 4 GB limit, so PCI address space is allocated below 4 GB. This means that any machine with 4 GB or more of physical memory has some of its physical memory “overlaid” by the PCI address space. If the memory controller of the machine supports remapping the overlaid physical memory to an address above 4 GB and if the processor is capable of accessing memory above 4 GB and if the operating system supports memory above 4 GB, then all of the physical memory is still usable. If any of the above are not true, then the “overlaid” memory is not accessible and the operating system will report less physical memory than is actually installed. For example a Windows server with 4 GB of physical memory installed might report only 3.5 GB of memory. In the case of IXS hardware, only type-model 2892-001 and 2892-002 are capable of accessing memory addr
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