Many users asking why hystou mini pc don’t support 3.5 inch HDD, except the mini pc size too small which not enough space for 3.5 inch HDD, the other important reason is power supply.
2.5 inch HDD power requirement is 5V only, but 3.5 inch HDD power requirement is 12V, so 3.5 inch HDD is not supported on hystou fanless mini pc.
And same reason to USB port, USB power is 5V only, so if you plug a big capacity 3.5 inch external HDD without extra power supply, it may not recognised by any USB port on any computers.
But if you do require using 3.5 inch HDD, you can consider some mini pc that comes with LVDS and COM port, cause their power supply is 12V too, if you dont mind the unprofessional for that kind power supply, you can use it for your 3.5 inch HDD, but we don ‘t sugest it, and dont take responsiblity for any wrong operation which brings troubles.