Is it possible to power SATA HDD by only 12V power adapter?
I found some 4pin molex to SATA adapter, but they are use 5V from Molex. I have onlu 12V power adapter. Can I use only 12V for SATA HDD?
If yes, what pinout can be for it?
Generally not, no.
However, it’s very easy to find out: Just look at your HDD’s label. There should be information on how much power it requires, stated separately for 5 V and 12 V. If it lists only 12 V, you’re probably good.
If you want to roll your own, get a 12-to-5-V DC-DC converter and you’re good. “UBEC” is a good keyword to find one.