Dell Precision T5400 User's Guide - Page 189

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. Removing Memory CAUTION: Before you begin any of the procedures in this section, follow the safety instructions in the Product Information Guide. 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 you purchased the new modules from Dell. If possible, do not pair an original memory module with a new memory module. Otherwise, your computer may not start properly. NOTICE: To prevent static damage to components inside your computer, discharge static electricity from your body before you touch any of your computer's electronic components. You can do so by touching an unpainted metal surface on the computer chassis NOTE: Memory purchased from Dell is covered under your computer warranty. Adding and Replacing Parts 189