Asus ITX 220 User Manual - Page 13

1.4 System memory 1.4.1 Overview The motherboard comes with two Double Data Rate 2 (DDR2) Dual Inline Memory Modules (DIMM) sockets. The figure illustrates the location of the DDR2 DIMM sockets: Channel Channel A Channel B Sockets DIMM_A1 DIMM_B1 1.4.2 Memory configurations You may install 512MB, 1GB and 2GB 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 the 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. • 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: - Use a maximum of 3GB system memory if you are using a 32-bit Windows® OS. - Install a 64-bit Windows® OS when 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 4GB on Windows® XP Professional x64 and Windows® Vista x64 editions. You may install a maximum of 2GB DIMMs on each slot. 1-4 Chapter 1: Product introduction