Asus P5E WS PROFESSIONAL User Manual - Page 40

2.4.2 Memory configurations You may install 256 MB, 512 MB, 1 GB, and 2 GB ECC and non‑ECC, unbuffered 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, it is recommended that you obtain memory modules from the same vendor. • If you install four 1GB memory modules, the system may only recognize less than 3GB of total memory because of address space allocation for other critical functions. This limitation appears on Windows® Vista 32-bit / Windows® XP 32-bit operation systems since it does not support Physical Address Extension (PAE) mode. . • If you install Windows® Vista 32-bit / Windows® XP 32-bit operation system, a total memory of less than 3GB is recommended. • This motherboard does not support memory modules made up of 128 Mb chips or double sided x16 memory modules. • Due to chipset limitation, this motherboard can only support up to 8 GB on the operating systems listed below. You may install a maximum of 2 GB DIMMs on each slot. 64-bit Windows® XP Professional x64 Edition Windows® Vista x64 Edition • 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. 2-14 Chapter 2: Hardware information