Dell Precision T3400 User's Guide - Page 159

NOTICE: If you remove your original memory modules from the computer during a memory upgrade, keep them separate from any new modules that you may have, even if the new modules were purchased from Dell. If possible, do not pair an original memory module with a new memory module; otherwise, your computer may not start properly. Install your original memory modules in pairs either in connectors DIMM_1 and DIMM_2 or connectors DIMM_3 and DIMM_4. NOTE: Memory purchased from Dell is covered under your computer warranty. Addressing Memory With 4-GB Configurations Your computer supports a maximum of 8 GB of memory when you use four 2-GB DIMMs; however, 32-bit operating systems, such as the 32-bit version of Microsoft® Windows® XP, can only use a maximum of 4 GB of address space. Moreover, certain components within the computer require address space in the 4-GB range. Any address space reserved for these components cannot be used by computer memory; therefore, the amount of memory available to the operating system is less than 4 GB. NOTE: The entire 8-GB memory range is available to 64-bit operating systems. The following components require memory address space: • System ROM • APIC(s) • Integrated PCI devices, such as network connectors, SAS controllers, and IEEE 1394 controllers • PCI or PCI Express devices/cards At start up, the BIOS identifies the components that require address space. The BIOS dynamically calculates the amount of reserved address space required, then subtracts the reserved address space from 4 GB to determine the amount of usable space. • If the total installed computer memory is less than the usable space, all installed computer memory is available for use only by the operating system. • If the total installed computer memory is equal to or greater than the usable address space, a small portion of installed memory is available for use by the operating system. Adding and Replacing Parts 159