Does the gigabit ethernet port on the Up Xtreme have automatic crossover or will I need to get a crossover cable if I am connecting two SBCs together.
Haven't personally tried this, but the Intel i210 ethernet controller has auto cross-over detect, so it should work just fine.
Twisted pair Ethernet PHY's must be correctly configured for MDI or MDI-X operation to inter operate. This has historically been accomplished using special patch cables, magnetics pinouts or Printed Circuit Board (PCB) wiring. The PHY supports the automatic MDI/MDI-X configuration originally developed for 1000Base-T and standardized in IEEE 802.3u section 40. Manual (non-automatic) configuration is still possible.
After checking, we wouldn't recommend you to use this function due to some compatibility issue
Therefore, automatic crossover is not supported by I210