Dell Precision T7400 User's Guide - Page 174

NOTICE: Do not install non-ECC or unbuffered memory modules. Doing so may cause the computer not to boot. NOTE: DIMM slots 1-4 have white latches for easy identification. DIMM slot 5-8 have black latches. Addressing Memory With 4-GB or Greater Configurations (32-bit Operating Systems Only) This computer supports a maximum of 32 GB of memory when eight 4-GB DIMMs are installed. Current 32-bit operating systems, such as Microsoft® Windows® XP and Windows Vista, can use a maximum of 4 GB of address space; however, the amount of memory available to the operating system is less than that installed. 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. The following components require memory address space: • System ROM • APIC(s) • Integrated PCI devices, such as network connectors and SCSI controllers • PCI cards • Graphics card • PCI Express cards (if applicable) At start-up, the BIOS identifies the components that require address space. The BIOS dynamically calculates the amount of reserved address space required. The BIOS 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 address 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 portion of installed memory is not available for use by the operating system. 174 Adding and Replacing Parts