Using lower profile heatsink from 2U systems in 4U ?

[Dr. Innovation]

I have multiple supermicro 4028-trt and just ebayed some 4029s in which I want to put GPU for my ML work.
To get my 4090 monster GPUs to fit in my 4028-trt (and expect to fit in the 4029's that I've ordered) I will need to reduce the height of the CPU heatsink.
I realize a lower-profile heatsink will not be as effective at cooling the CPU, and I'm running close to top of the line CPUs (well ES/QS version of them), e.g. my 4028s have E5-2699v4 in them and the 4029s will have 8280s (ES). How bad will it be to reduce from the stock 65mm height to 27-30mm height. I'll note they run the low-profile in 1U and 2U systems which can still be configured with those processors so I hope (expect?) they will be okay.

Could I use a SNK-P0047PS+ or another 47 series heatsinks in place of the 4028s SNK-P0048PS? and use a SNK-P0067PS or other 67 series in place of the SNK-P0068APS4 in my 4029?

Should I look at adding a small fan on them, e.g using something from a laptop (I can afford maybe 15mm ontop of the heatsink).

 

[olev]

If you're not worried about noise, the active dynatron 1U coolers (e.g. R25 for Socket 2011 Narrow, for example) are very effective.
That way you can get more cooling performance out of the same height than going with a smaller passive heatsink.

 

[nexox]

Dynatron also makes active 2U coolers, if you have the space you might as well go for that vs 1U active. Passive coolers are going to require some air guides or something to force the case fan exhaust through the fins, otherwise it will mostly go around. If you already have 2U passive heatsinks and want to add a fan, place it in front, blowing through the fins towards the back of the case, not on top.

 

[Dr. Innovation]

If you're not worried about noise, the active dynatron 1U coolers (e.g. R25 for Socket 2011 Narrow, for example) are very effective.
That way you can get more cooling performance out of the same height than going with a smaller passive heatsink.

Dynatron also makes active 2U coolers, if you have the space you might as well go for that vs 1U active. Passive coolers are going to require some air guides or something to force the case fan exhaust through the fins, otherwise it will mostly go around. If you already have 2U passive heatsinks and want to add a fan, place it in front, blowing through the fins towards the back of the case, not on top.

Great thanks to both of you. I am not worried about noise.. there are 60+ GPUs in that rack and it always sounds like jets are taking off.

I was only looking at supermicro branded but if these work that is great. I presume the 2U would be better at cooling. but I've not found any that are short enough all I've seen are 60mm high which is what the stock passive one is.. DO you known any shorter ones?

Are different socket coolers standard for the same processor (I can see why they would but never used any but the server's suggested ones). E.g. So for the 4029 would something like a DYNATRON B3 INTEL® SOCKET FCLGA3647 1U ACTIVE

 

[nexox]

Ah I misread your post initially, you're going to want a 1U active cooler to fit that height, and you need it to fit the specific socket, which (at least with Intel) often comes in two ILMs: narrow and square. Some coolers come with multiple brackets to fit different ILMs, you just need to figure out which you have and confirm that whatever you buy fits it.