Asus P5QPL-VM EPU User Manual - Page 22

1.7.2 Memory configurations You may install 512MB, 1GB, 2GB, and 4GB unbuffered non‑ECC DDR2 DIMMs into the DIMM sockets. • You may install varying memory sizes in Channel A and Channel B. The system maps the total size of the lower-sized channel for the dual-channel configuration. Any excess memory from the higher-sized channel is then mapped for single-channel operation. • Always install DIMMs with the same CAS latency. For optimum compatibility, we recommend that you obtain memory modules from the same vendor. • Due to the memory address limitation on 32-bit Windows® OS, when you install 4GB or more memory on the motherboard, the actual usable memory for the OS can be about 3GB or less. For effective use of memory, we recommend that you do any of the following: - Install a maximum of 3GB system memory if you are using a 32-bit Windows® OS. - Use a 64-bit Windows® OS if you want to install 4GB or more memory on the motherboard. • This motherboard does not support DIMMs made up of 256 megabits (Mb) chips or less. • This motherboard supports up to 8GB memory modules on Windows® XP Professional x64 and Vista x64 editions. You may install a maximum of 4GB DIMMs on each slot. • The default DIMM frequency depends on its Serial Presence Detect (SPD), which is the standard way of accessing information from a memory module. Under the default state, some memory modules for overclocking may operate at a lower frequency than the vendor-marked value. To operate at the vendor-marked or at a higher frequency, see section 2.4 Advanced menu for manual memory frequency adjustment. • For system stability, use a more efficient cooling system to support a full memory load (2 DIMMs) or overclocking conditions. • Some old-version DDR2-800 DIMMs may not match Intel®'s On‑Die‑Termination (ODT) requirement and will automatically downgrade to run at DDR2-667. If this happens, contact your memory vendor to check the ODT value. • Due to chipset limitation, DDR2-800 with CL=4 will be downgraded to run at DDR2-667 by default setting. If you want to operate with lower latency, adjust the memory timing manually. 1-12 Chapter 1: Product introduction