As discussed in this article (by oz_paulb) on the xboxhacker.net forums, this appears to be a Atmel 25020 EEPROM. The chip from the 1stgame article reads: ATMEL524 25020AN SU18 Datasheet can be found here[atmel.com] [/QUOTE]
XboxHacker.net also posted an xexdumper utility (for linux) that was released by oskie on IRC. You can download it here.
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