for a riser barely using 10watts they'd probably do fine?
I'm using ASRock H110 Pro BTC+ & as soon as I connected my 3rd GPU it told me to give it more power via molex. I would never try to power a GPU with molex or SATA, I'm just looking at powering the last 2 risers(10 watts each) off of a 2x molex to 2x 6 Pin connector.
I am curious what others use or what best practice is, if there is one?
Thanks!
Allow me to explain the concept of a powered riser a little bit more clearly:
During typical use, a graphics card installed directly into the motherboard will draw power from both its onboard PCIe power connections (if any) AND through the motherboard's PCIe slot itself.
Back in the day, most people used PCIe x1 to x16 ribbon risers. Some of those were unpowered risers, meaning each card would pull some of its power through an x1 slot instead of a full x16 slot. Turns out that this didn't work so well for multi-card setups on some motherboards. *insert horror stories*
A good powered riser should allow you to provide the graphics card with power through the slot on the riser, most of which was never pulled through the motherboard.
To put it simply, when you are plugging in the power connectors for your risers, you are not just powering the riser itself (although yes, I'm sure it uses a little bit of power for itself), but you are also providing power for the graphics card. It's difficult to determine exactly how much power is drawn through the slot vs. through the card's onboard PCIe power connectors. Do note that AMD has sometimes gone over-spec with how much power goes through the slot (
https://www.pcper.com/reviews/Graphics-Cards/Power-Consumption-Concerns-Radeon-RX-480).
Quality molex connectors handle going over-spec quite well. SATA is more controversial.