Installing smaller heatsink than CPU heatspreader

[EBE2]

Hello everyone,

I got a Zalman CNPS5x Performa which has a heatsink surface of 32x32mm, for my Phenom 955 which (I later noticed) has a heatspreader of 36x36mm. The question is: what's a good way to install the HS in this case? (It should be fine since FrostyTech explicitly lists as testing this HS with 36x36 AMD CPUs, and the Phenom is on the HS compatibility list.)

On my initial install, I tried to fill in the edge gaps with thermal paste so that they reach the HS as much as possible, not sure if that's the best idea. I am asking since I am getting less-than-ideal temps (40 idle, up to 80 degrees under long-term load on all cores with Orthos Prime). The case is also rather cramped since I needed a small case, which also forced me to buy this cooler rather than a larger one which might work better for my 125W TDP, so there will be some unavoidable hit due to that, but I just want to do the best job possible under the constraints.

Thanks in advance!

 

[synphul]

It should be fine, most of the heat is in the middle of the cpu heat spreader. Just apply thermal paste like normal, either a rice grain/pea sized amount in the middle or a couple thin lines in an "X" shape work decently. Try not to use too much, it just needs a very fine layer. If you have a metal straight edge, you can try removing the cooler and cleaning the thermal paste off everything with rubbing alcohol (isopropyl) then check the base of the zalman cooler with the metal straight edge on edge across it to make sure it's decently flat (no gaps, humps). Sometimes 'lapping' a heatsink can help. Don't worry about adding thermal paste to the small ledge of the cpu heat spreader where it sticks out 1mm from the base of the cooler, it won't add to the cooling value and will likely just make a mess.

Ambient room temps, too much thermal paste, a cramped case with low airflow are all things that can contribute to higher cpu temps. What are room temps like? If you can increase airflow in the case it will likely help. Stronger fans for more airflow, not sure which case you used or how many fans or where they're supported.

 

[EBE2]

(deleted, posted an answer by mistake instead of replying)

 

[EBE2]

It should be fine, most of the heat is in the middle of the cpu heat spreader. Just apply thermal paste like normal, either a rice grain/pea sized amount in the middle or a couple thin lines in an "X" shape work decently. Try not to use too much, it just needs a very fine layer. If you have a metal straight edge, you can try removing the cooler and cleaning the thermal paste off everything with rubbing alcohol (isopropyl) then check the base of the zalman cooler with the metal straight edge on edge across it to make sure it's decently flat (no gaps, humps). Sometimes 'lapping' a heatsink can help. Don't worry about adding thermal paste to the small ledge of the cpu heat spreader where it sticks out 1mm from the base of the cooler, it won't add to the cooling value and will likely just make a mess.

Ambient room temps, too much thermal paste, a cramped case with low airflow are all things that can contribute to higher cpu temps. What are room temps like? If you can increase airflow in the case it will likely help. Stronger fans for more airflow, not sure which case you used or how many fans or where they're supported.

Thanks for the detailed advice. I removed, cleaned, and reinstalled the HS with a "regular" thin layer of paste, and increased the velocity of the case fan to 800RPM (max is around 1000 but it's becoming noisy at that level). So far, no big change in temperatures, so I guess these are the limits of my small case and HS...

Oh well. Under "regular" load (Witcher 3), not stress testing, the cores hover between 60-65 degrees, and the recommended max temp from AMD is 62, so I guess it's fine... The CPU lasted 4 years already with the stock fan so it'll hold a while longer.

PS: Noticed I didn't answer the questions. Room temps are ~25 degrees Celsius this time of year. The case is a CoolerMaster Elite RC-342, it has a front fan which is the one I mean above.