According to Intel spec; Dual channel DDR can be named as channel A and B. In 8INXP, dimm slot 1 and 3 are channel A, dimm slot 2 and 4 are channel B. Dual channel mode will only work with DDR memory modules inserted in dimm slot 1&2 or dimm slot 3&4. DDR memory inserted in dimm slot 1&4 or 2&3 will only work as single channel mode, and only channel A is available. Memory in channel B will not be detected.
Yes, please update the latest BIOS. But please note if your OS like WinXP is already installed on SATAHDDs under ICH5R controller, please make sure to update ICH5RSATA RAID driver from our IUCD 2.4 or Gigabyte website first, then update the latest BIOS.