MiSTer FPGA Forum

I have a stock fan, and I'm pretty sure it runs at 5v by default. I see a lot of people mentioning "running fans at 3.3v" to reduce fan speed since with a decent heat sync you're probably fine on cooling. I thought it might be a nice way of reducing noise without needing to buck up and get a Noctua. How is this done?

To my recollection, the IO board has a jumper to set the fan voltage to 5.0 volts or 3.3 volts.
My set has already a switch to select one or the other speed, I guess this switch is connected in lieu and place of the jumper.
Pay attention that maybe not all 5.0 volts fans are capable to start to turn with 3.3 volts.

Edit: Found the confirmation of this at least for the IO v6.1 from ultimate mister (the one I have )
https://ultimatemister.com/product/i-o-board-6/

Look at this PDF : https://github.com/MiSTer-devel/Hardwar ... rd_6.1.pdf
At the left side, almost at the middle height, there is the FanSW to select the fan voltage (could be a jumper in case the switch is not installed I guess or depending of the revision of your IO board)

I set my 5 volt RGB fan to 3.3 volt this way (6.1 board) and even the RGB effect still works fine. The fan is a whole lot more quiet this way and still cools sufficiently.

kathleen wrote: ↑Tue Mar 14, 2023 5:46 am

To my recollection, the IO board has a jumper to set the fan voltage to 5.0 volts or 3.3 volts.
My set has already a switch to select one or the other speed, I guess this switch is connected in lieu and place of the jumper.
Pay attention that maybe not all 5.0 volts fans are capable to start to turn with 3.3 volts.

Edit: Found the confirmation of this at least for the IO v6.1 from ultimate mister (the one I have )
https://ultimatemister.com/product/i-o-board-6/

Look at this PDF : https://github.com/MiSTer-devel/Hardwar ... rd_6.1.pdf
At the left side, almost at the middle height, there is the FanSW to select the fan voltage (could be a jumper in case the switch is not installed I guess or depending of the revision of your IO board)

Right, I have the exact same one as well. So is there a switch on the bottom side of the board? I just popped off the top of my case to take a look but based on the diagram JP3V/JP5V should be on the bottom. I see the product page even mentions there's a selector for 5/3.3 volts on the fan. Is it just a small little switch on that part of the diagram? I just want to make sure I know what to look for before I dissassemble my MiSTer.

naylord wrote: ↑Fri Mar 17, 2023 3:20 am

kathleen wrote: ↑Tue Mar 14, 2023 5:46 am

To my recollection, the IO board has a jumper to set the fan voltage to 5.0 volts or 3.3 volts.
My set has already a switch to select one or the other speed, I guess this switch is connected in lieu and place of the jumper.
Pay attention that maybe not all 5.0 volts fans are capable to start to turn with 3.3 volts.

Edit: Found the confirmation of this at least for the IO v6.1 from ultimate mister (the one I have )
https://ultimatemister.com/product/i-o-board-6/

Look at this PDF : https://github.com/MiSTer-devel/Hardwar ... rd_6.1.pdf
At the left side, almost at the middle height, there is the FanSW to select the fan voltage (could be a jumper in case the switch is not installed I guess or depending of the revision of your IO board)

Right, I have the exact same one as well. So is there a switch on the bottom side of the board? I just popped off the top of my case to take a look but based on the diagram JP3V/JP5V should be on the bottom. I see the product page even mentions there's a selector for 5/3.3 volts on the fan. Is it just a small little switch on that part of the diagram? I just want to make sure I know what to look for before I dissassemble my MiSTer.

Mine doesn't have a switch, so it is just a matter of shifting the jumper over one position. It is located at the top side of the board, next to the fan connector.

Ah yeah, found the jumper. I actually learned what a jumper is doing this just now. It slid off and went to the other pegs easily. I was startled when I botted it up though and it sounded like a jet engine! It turns out, the jumper came configured on the 3V and I just moved it to the 5V! Oh well, I moved it back but now I guess if I want it to be silent I'll need to buy a premium fan.

Thanks for the help

I have a standard hamburger with heatsink, works fine without a fan give it a try.

I want to run my noctua fan also at 3.3V that should work right? My I/O Board is missing the fan header Stupid question but which Jumper do I need to buy? It seems there are 2 versions what are their differences?

From the pictures either type will work they are just open and closed tops for the jumper/shunt, that is the only difference.

Can a Noctua 5V Fan reduced to 3.3V or doesn't it turn on?

ADV7842 wrote: ↑Sun Mar 31, 2024 8:06 am

Can a Noctua 5V Fan reduced to 3.3V or doesn't it turn on?

Yes, the 5 Volt Noctua starts and spins fine on 3.3 Volts.

To be honest I have never heard my Noctua at 5v. People must have better hearing than me!

FPGA64 wrote: ↑Sun Mar 31, 2024 8:44 pm

To be honest I have never heard my Noctua at 5v. People must have better hearing than me!

I guess so I've been using my Noctua for 2 years on 5V and 3.3V is a quality of life upgrade for my sensible ears at least I get that it's not for everyone depends preferences and on the environment etc.

I haven't tested it to the max but even at 3.3V temps should be fine (?) I ran my board without a fan and it and after 1h it was significally hot. not the case even with 3.3V

I would hear my Noctua fan at 5v. At 3.3v it is silent.

Lloyd2084 wrote: ↑Sun May 12, 2024 8:09 pm

I would hear my Noctua fan at 5v. At 3.3v it is silent.

You and me, buddy.
Works great on 3.3v pins.