Just for whoever is interested - I’ve found this company to do custom heatsinks and blocks for RAM: Custom RAM copper heatsinks for DDR5 / DDR4 - Bartxstore
Ordered for my build. Fingers crossed.
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Here’s what the Bartx ram heatsinks look like after you mill holes into them so that they can fit over the extra tall inductors RDIMMs have on them:
and the drawing for if you want to mill the pockets yourself:
I still haven’t heard from them after placed the order 
But now you made me more worried. If I have to mill that part, why did he said they have the right pocket for those components? o.O
Also, that part is a huge source of heat. If they require this milling and will be exposed that makes sort of useless the cooling alltogether 
Looks like they’re backordered. He might need to produce them before proceeding with the order. I got a shipment notification 10 days after I got an order number, but they were in stock when I ordered mine.
It’s got the right sized pockets for normal unbuffered “client” DDR4/DDR5 with the small client power circuitry.
Registered DDR5 has multiple options for PMICs, all of which can output more power than the “client” PMICs
“Low-Current” PMIC = 15.3w
“High-Current” PMIC = 25.5w
“Extreme-Current” PMIC = >25.5w (this is what MRDIMMs use)
The beefier power management on the RDIMMs requires the huge inductors which causes the problems with normal client ram heatsinks.
The inductors don’t get nearly as hot as the ICs on the ram, also they can tolerate temperatures ~50C higher than the DRAM IC without degrading performance or longevity:
(kind of hard to tell what is going on in this picture, but the two hot spots in the middle are the inductors looking through the two holes made as shown in the post above)
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Ahh. Backorder. I didn’t noticed that on the site.
But nonetheless, they should have been in touch to give some expectations on when it would be available.
On a side note - do you know any other alternative?
Thanks as always for the valuable input.
@Zoson found some heatspreaders that fit DDR5 RDIMMs, but they don’t seem to be available anymore (even on aliexpress):
I’m planning on doing a run of tall, aluminum, air cooled finned heatsinks for DDR5 RDIMMs (which I hope should be cheap) because I’m doing a 16 DIMM system and don’t want to spend too much.
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Yeah, Air for me doesn’t work must be water because of the noise.
I think I guess I’ll have to pay someone to design it from the measurements and send to PCBWay to manufacture it. Will not be cheap, but at least the memory will work. Then I can get any available block, like the ones from Alphacool.
There are no fans on the heatspreaders and they arn’t required for stable operation. So there is no noise.
I don’t think the heatspreader will make that much of a difference without proper airflow to move the heat out. The whole purpose of my setup is to have as minimal fans as possible to not have noise, hence why water cooling is the solution for me. The only fans goes into the radiators in my case.
I’ll share the 3d model I come up with for the DDR5 RDIMM heatsinks once I make it. You could modify them or use them as a sanity check for yours.
I think the most difficult dimension on them is going to be the pocket for the inductors, getting it’s height and placement correct.
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I’ve found the EK memory block on TitanRIG and ordered it since the other one you suggested the guy doesn’t reply. I’m pretty sure the pocket will not fit but, I’ll have a base to open and cut it. If you have the 3d model perhaps I can ask PCBWay to make one for my in full coper.
Are they the EK monarch heatksinks?
you could probably even get away with aluminum for the memory sinks since the fluid would be contained within the block that mounts to the memory heatsinks.
https://www.ekwb.com/shop/ek-quantum-momentum2-quad-ram-module-set-d-rgb
Ignore the “RGB” will strip it out.
Yes, aluminum would looks nice as I can use anodized black pounder on it. But if copper perform better, copper will be.
There’s also a middle ground called chromium copper that performs halfway in between aluminum and pure copper, its benefit is that it doesn’t tarnish like pure copper does.
Hey, this is what I’ve got so far.
Made the whole piece following the dimensions of the heasink from EK’s block kit.
“Printed” in resin just for a fitment test where instead of cutting the pockets I’ve just made them .3mm deep. That allowed it to fit a .5mm thermal grizzly thermal pad perfectly. Everything else is padded with a 1mm pad and make great contact while mechanically fitting on the RAM flush.
I’ll now order it on PCBWay and wait for arrival. Tbh, I don’t even need to order both parts. Only the one where the pocket was made since the back of it, already sit flush on the original piece.
Meanwhile, this is how the new build is going:
The two inner loops in the middle of the manifold (the ones which are not quick disconnect) are temporary while the new GPUs which will be added to the loop don’t arrive. The loop for now is dead silent under heavy load 
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if this is your rig… you have more than enough fans to have sufficient airflow to allow passive heatspreaders for your memory to work. way more than enough!
Yes, this is my rig. But no, the airflow is not enough. I’ve been trying it.
I’ve designed the heatsink for the modules. Got the first production batch and it was off by 2mm. The new corrected batch is in production now. Should arrive early next year. Hopefully all will be done early next year and the RAM will be in descent temps. Fingers crossed.
I have finally received and installed the modules.
The temps went down on the DIMM modules from 80-90C to 40C under load running benchmarks!
Here are some pictures of the end build:
If anyone is interested on manufacture yours, just feel free to use the models I’ve open sourced here: GitHub - galvesribeiro/ddr5-rdimm-heatsink: DDR5 RDIMM heatsink design files
Now All its needed on this build is the 2x RTX 5090 and its respective blocks 
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Sir this is amazing. I am about to order 80 (yes) of these from PCBWay. Will probably go with copper.
I’ll probably draw up two passive heatsinks that can be bolted on top of groups of 4 and 6 of these.
Just one question: what thermal pads are you using for the RAM? Asking mainly about thickness, but if you have a specific product you can recommend that’s cool too.
Thanks!
I’m using the ones that came with the EKWB memory block which are 1mm thick (the blue one). In the PMCI specifically I’m using one for DerBauer “Thermal Grizzly Minus pad 8” which is 0.5mm since they are very thin and delicate (the pink one).
If you are going passive cooling, then yes, copper would probably have a better performance. Since I was going for water, I did picked up aluminum as it would make very minor difference in thermal performance but the cost would be significantly cheaper.
Glad it helped
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