Dell OptiPlex GX620 - Manual (Page 54)

Addressing Memory With 4-GB Configurations
This computer supports a maximum of 4 GB of memory when you use four 1-GB DIMMs or two 2-GB DIMMs. Current operating systems, such as Microsoft®
Windows® XP, can only use a maximum of 4 GB of address space; however, the amount of memory available to the operating system is less than 4 GB.
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:
l System ROM
l APIC(s)
l Integrated PCI devices, such as network connectors and SCSI controllers
l PCI cards
l Graphics card
l 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.
l 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.
l 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.
Removing Memory
1. Follow the procedures in " Before You Begin ."
2. Carefully press out the securing clip at each end of the memory module connector.
3. Remove the memory module.
Replacing/Adding Additional Memory
A matched pair of memory modules in connectors DIMM1 and DIMM2 (white securing clips)
B matched pair of memory modules in connectors DIMM3 and DIMM4 (black securing clips).
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. You should install your original memory modules in pairs either in connectors DIMM1 and DIMM2 or
connectors DIMM3 and DIMM4.
NOTICE: Removing memory modules from DIMM2 and DIMM4 on the desktop computer requires you to remove the optical drive (see " Drives "). Failure
to do so may cause damage to the memory module and the DIMM socket.
NOTE: Memory purchased from Dell is covered under your computer warranty.
1 memory module
2 securing clip (2)
CAUTION: Before you begin any of the procedures in this section, follow the safety instructions in the Product Information Guide.
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.