sata numbering convention

schwendemann wrote: purchased z270 supercarrier and using m2 ssd. manual says that the m1 slot disables sata3_0. the manual doesn't show that sata number. which sata device is sata3_0

You're right, it sure doesn't identify all the SATA ports appropriately in the Motherboard Layout figure in the full manual on your board's download page:

http://www.asrock.com/mb/Intel/Z270%20SuperCarrier/index.asp#Manual

I assume your question is which port is the Intel SATA3_0 port?

If you check the manual above, in the Onboard Headers and Connectors section, starting on page 24, you'll find this figure on page 25:



The SATA3_2, SATA3_3, SATA3_5, etc ports are closest to the mother board, and the SATA3_0, SATA3_1, SATA3_4 ports are above them, respectively.

The SATA3_0 and SATA3_2 ports are the two ports at the very top of the stack of ports, viewing the board as mounted in a standard PC case.