Noctua 40mm NF-A4x20 FLX or PWM? (for flex atx psu)


Cable Smoosher
Original poster
Jul 22, 2017
I have the Flex ATX Enhance ENP-7660B coming. As I understand it I can replace the stock fan in one of two ways.

1. Use the 3 pin FLX fan and connect it to the original psu internal header.

2. Use the 4 pin PWM fan, connect it to the motherboard and set a fan curve through software.

Can someone experienced with this give me an idea which would be the better approach? Thanks.


Chassis Packer
Apr 20, 2018
Internal header is always the better approach to PSU Fan modding as the Motherboard has no idea about PSU thermals, but the PSU does. Some PSUs don't have a decent fan control though so improvement might be minimal.

I'd give the internal approach a try and if it doesn't work switch it to the motherboard.

You can use 4-Pin Fan for both internal and external connection so i'd go for the PWM version. They both come with the same adapters (2-pin internal) and connectors.
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Master of Cramming
Jul 31, 2019
There are motherboards that can take an external temp sensor (asus x570-I rog gaming for example) and you can draw your own curve based on that sensor (that you can place inside the psu) also you can use a fan controller like a aquacomputer quadro, that can take several temp imputs and control up to four different fans each of them with a different curve related to a different temp.