I have been using my hdplex h5 for 9 years now (!!!), went through many builds. My current desktop is a 13900T with an RTX 3060, all fanless; 99% of the time, it's been great. I realize after such a long time that on occasion (1% of the time), I want all the compute power that this build has and I can't extract it from this build due to thermal throttling. The motherboard is a bit old (h670) and I need thunderbolt. So now I'm planning to use the opportunity that the motherboard upgrade brings to "semi-silent" or "silent almost all of the time", with a Jonsbo Z20 + NH-P1, keeping the CPU but using an ITX z790 mobo I bought in ebay. Planning to inlcude an undervolted gtx 5060Ti dual fan with "0dba support" (no fans below 50 degrees), and two noctuas, intake at the bottom of the case and exhaust at the rear. Fanless PSU (seasonic, 500w). My desktop OS is linux. Home desktop machine. A little steam gaming. A lot of photo editing (#darktable) Anybody in the community with experience in nh-p1 / semi-silent builds that can share real-world experience, will it able to handle 106W (13900T peak) keeping the CPU below throttling?
Not sure why you're so tied to a (mostly) fanless build with the upgrade. In my experience, ITX cases need airflow, because most cases aren't designed with fanless operation in mind (unlike your h5).
The NH-P1 does fine with 65W CPUs, but I think you will be disappointed with 105W+ options, especially if you have desires to push your parts a little. Additionally, it performs best with some active airflow, however slight.
I understand the want for quiet operation, so as someone who tried a 65W cooler on a 105W CPU, just get a better cooler. I'm running the Phantom Spirit 120 SE with Noctua fans on an undervolted 5700X3D, got a triple fan 3060ti TUF GPU (with fanstop), a 650W Cooler Master PSU (with fanstop), dual top exhaust Noctua fans, and I'm running custom fan curves with CoolerControl (I'm on Linux, too).
The whole thing sits about a foot from me, and I barely hear it with bare ears. With my non-ANC headphones, I don't hear it at all, unless I'm stress testing it.
Personally, with how hardware prices are going, I wouldn't trade the peace of mind of active cooling for the diminishing returns of passive silence, especially if I planned to actually push the parts at all. Keep those parts cool and working; don't make them rely on their built-in thermal throttling!
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