2U becomes really tricky with CPU’s with desktop levels of power. Here is what I did with my Ryzen 9 5950x. It’s not a 14900k, but it might give you an understanding of the problems you’ll tun into, and might give you some ideas to help solve them.
So, I recently put a 16C/32T Ryzen 9 5950x installed in an Asrock Rack x570-D4U in an old Supermicro CSE826 2U case, and I struggled.
The way these shipped from the factory, you are supposed to lay a plastic shroud down over the motherboard that focuses the airflow from the right two high RPM loud Nidec UltraFlo fans that are installed in the center fan wall over the passive heatsink.
This does work, but it is anything from quiet. Those Nidec UltraFlo fans can wake the dead.
So I decided to be creative. I bought a few Arctic p80 Max. The “Max” being the operative word here. The regular p80’s or something that is quieter like Noctuas will never work here.
Then I modded the fan carriers to fit the fans to the center wall (the Nidec Ultraflo fans are 38mm thick, but the Arctic P80 Max fans are 25mm thick, sealing around them with HVAC Foil tape to make sure that the air doesn’t leak back around the center wall, and instead gets a linear one way flow as intended.
I even found a weird sized 70mm fan in my parts bin which was just large enough to fit well in the rear of the case and exhaust some air out of the half height PCIe slots to help keep my HBA cool.
The server this replaced was a 4C/4T Rocket Lake Xeon E-2314. It was much lower power than the Ryzen, and as such was able to get away with a ID Cooling IS-55 cooler.
I didn’t want to use the shroud + fanwall + passive heatsink approach to cooling this one, as that was going to be loud. I also didn’t want to buy a little Dynatron or Supermicro active 2U heatsink, as those tend to use small heatsinks and little 60mm fans at incredibly high RPM’s and they are unpleasantly loud. So I wanted to try to use this IS-55 desktop cooler I already had instead.
The IS-55 is great for its size, actually surprisingly so, but it is a small cooler. I searched high and low for other coolers that would fit in a 2U case, but the others were either more compact and worse, or too tall to fit with a fan attached. It was going to have to be the IS-55.
I knew this heatsink was never going to keep up with the Ryzen as it was. I wanted to put a higher airflow fan on it, but all the best ones are 25mm thick, and then the top of the fan winds up being so close to the lid that it starves it for air, so you need a slim 120mm fan.
The highest performance 15mm thick 120mm fan I could find was the Silverstone AirSlimmer 120, so I bought one of those.
The next problem was that when installed on the Asrock Rack x570-D4U the ID Cooling IS55 wound up being oriented the wrong way. The airflow in the 2U case is front to back, but its find were oriented side to side.
So I wound up fabricating my own mounting brackets for the thing so I could rotate it 90 degrees so it would line up with the air flow. Most of the air flow cooling the CPU was going to come from the Airslimmer fan on top of the heatsink, but I didn’t just want to have the broad side of the heatsink blocking air, so I figured rotating it was the right thing to do.
This took several tries, but eventually I converted the Intel brackets the unit came with into 90degree rotated AMD brackets, by drilling some holes, and using some metal epoxy to secure some screws in place.
After a lot of trial and error, I eventually got it to the point where the custom mounting brackets were resulting in a good flush mount.
This still was not enough.
Idle and low load speeds were fine, but even with the Air Slimmer at 100% speed on top of the heatsink the slightest amount of load would would send the CPU quickly shooting up to 70C.
It was completely usable, but it was alarming to see even light loads shoot that high that fast, and have it sit thermal throttling against the max temp.
At first I thought my custom mount was bad, and spent a lot of time troubleshooting that but pasting it, and mounting it, and then taking it off again, showed evidence of a perfect mount.
I also installed a Honeywell PTM phase change sheet instead of thermal paste, and this did shave a few degrees off, but it didn’t significantly change the situation.
The interesting part is that high all core loads were actually quite reasonable, but normal bursty low threaded loads would cause it to peak like crazy.
I found and set ECO TDP mode in the BIOS which limits it to 65W, and this - again - helped a little, but not enough to make me happy.
Then I remembered something. These Ryzen CPU’s aggressively increase voltage to and boost clock speed to their best cores in lightly threaded loads. I wonder if it is just the boost behavior that is messing me up?
And that is exactly what it was. I used the linux command line program “cpupower” to limit the turbo clocks to 4Ghz, and instantly the problem went away. All core loads were still no problem, and lightly threaded loads also no longer caused the temps to spike like crazy.
Then I started walking it up. I found that I could set the max turbo clock to 4500Mhz and still have it stay at a civilized temperature.
After I found the sweet spot, I created a systemd service file to start the limiter on every boot.
Now I’m able to slow down the fan wall to the point where the case temps are decent, and volume levels are much more reasonable.
Here we are during pretty average load: (the type of load that would have been low threaded and spiking like crazy before)
k10temp-pci-00c3
Adapter: PCI adapter
Tctl: +53.4°C
Tccd1: +52.8°C
Tccd2: +43.2°C
nvme-pci-0100
Adapter: PCI adapter
Composite: +41.9°C
nvme-pci-2300
Adapter: PCI adapter
Composite: +38.9°C
Those two NVMe drives look like they are running hot, but never mind them. They are Optanes, and Optanes by their very nature run hot.
It’s still not the quietest system I’ve ever had. No 2U system is ever going to be. These are not the kinds of cases you use for something that you work within earshot of, but at least it no longer sounds like a Jumbojet preparing for takeoff.
I have used three different 2U cases since I have been home labbing.
The first was an old HP DL180 G6 I nicknamed the Dreamliner, because it literally sounded like a jumbojet preparing for takeoff. I had it in my basement at the time, and I could hear it two stories up in my bedroom with all doors closed in between. I tried modding this thing but was never successful, and eventually abandoned it.
The second was the case the previous Xeon E-2314 was running in, a cheap iStarUSA D-214-MATX I got on Newegg. This one was reasonable, because the little quad core Xeon didn’t produce much heat. I ran it with Noctua 80mm fans with no problem.
And now there is this Supermicro case.
In general the wisdom is that unless you use fancy (and risky) 80mm water cooling radiators, a 2U case can be quiet with a low power CPU, and you can get creative and tame higher powered CPU’s to run more quietly in them, but they are never going to be as quiet as a desktop. It’s just the nature of the beast.
Sadly I forgot to take any pictures at all throughout this project, so I have noting to post here 
I have to install a new NIC in it (I’m replacing the dual port x520 with a quad port x710) in the near future. If you are curious to see what my implementation looks like, let me know and I’ll see if I can take a few pictures and add them here.