Hmm... I put my 5 cents on that the X is x as in xena as xorro. And the resemblance of "xorro" and "zorro" can't be ignored. The Xorro slot seen on the mobo on the pictures is clearly to small to fit a Zorro card (100 pins, right?). So maybe it's for a raiser-card/doughter board for fitting old Zorro cards on this mobo. And the Xena-chip location would indicate that it's controlling the Xorro slot.