An Microsoft manufactured motherboard running a specilized "ARCADE" kernel. these boards are probably overproduction developmentkits rebuild or on purpose to become arcade systems.

Instead of the MCPX X3 found in all retail xboxes, these are fitted (like the development kits) with X2 chips, this means that a kernel on the TSOP should account for this missing "hidden" bootrom.

The SMC pic chip still requires the right challenge so but is a differnt version from retail hardware.