Adding and Replacing Parts 189less than that installed. Certain components within the computer requireaddress space in the 4-GB range. Any address space reserved for thesecomponents 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 spacerequired. The BIOS then subtracts the reserved address space from 4 GB todetermine the amount of usable space.• If the total installed computer memory is less than the usable addressspace, all installed computer memory is available for use only by theoperating system.• If the total installed computer memory is equal to or greater than theusable address space, a portion of installed memory is not available for useby the operating system.Removing MemoryCAUTION: Before you begin any of the procedures in this section, follow thesafety instructions in theProduct Information Guide.NOTICE: If you remove your original memory modules from the computer during amemory 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 originalmemory module with a new memory module. Otherwise, your computer may notstart properly.NOTICE: To prevent static damage to components inside your computer, dischargestatic electricity from your body before you touch any of your computer’s electroniccomponents. You can do so by touching an unpainted metal surface on thecomputer chassisNOTE: Memory purchased from Dell is covered under your computer warranty.
