Improper contact between CPU and cold plate?

[Chen G]

I have an EK monoblock on my 3950x, I used liquid metal as TIM.

I have so much water and cooling water temperature is basically constant at 24 degrees unchanging.

So first of all CPU temperature is like 32 idle minimum, seems a bit high for liquid metal.

Load temperature is over 64 degrees at 165W SOC+Core power, again seems high for less than 200w CPU with solder and liquid metal.

 

But the real strange thing is after the CB run is done, it takes like 20 seconds for it to get back down to 3X degrees idle temperature, and I don't remember seeing this with my old system. From what I can remember water cooled GPU basically fall instantly back to liquid temperature once the load is off, CPU has IHS so probably not as quick but I don't think it should like 20 seconds should it?

 

At first I thought it was a flow rate issue, like the block got heated to like 50 degrees, but I boosted flow rate and there's basically no difference, it takes just as long to get back down to ambient. So what's going on here?

I had trouble with LM because the ryzen IHS doesn't stick at all, luckily the cold plate does so I just tried to put a layer of it on the cold plate only. Could it be that for example the cold plate and the IHS is only partially connected with liquid metal, and there's an air gap above where the chips are?

 

Also how come I can't get PBO to go above ~160w, I set the power and current limits to over 200 but it stops boosting at ~160w.

[Deli]

Liquid Metal will only drop 2C compares to good thermal paste if you use it on IHS and cold plate.

 

I have a 3900X. Same 32C idle temp as yours but with Kryonaut. Load temp is 72C with a 280mm AIO.

[Chen G]

8 hours ago, Deli said:

Liquid Metal will only drop 2C compares to good thermal paste if you use it on IHS and cold plate.

 

I have a 3900X. Same 32C idle temp as yours but with Kryonaut. Load temp is 72C with a 280mm AIO.

But how long does it take to drop to liquid temperature after the load is off?

[valwar]

On my 3900x and a EKblock it also takes like 18sec for the temps to go down from 66c to 39c

So it looks quite the same

[Deli]

4 hours ago, Chen G said:

But how long does it take to drop to liquid temperature after the load is off?

This is the part I don't get. Mine is like around 10 second. I do notice Intel CPU will drop back to idle temp very fast, like 2-3 second, after a heavy work load. And the idle temp is only 6-7C above ambient temp. So usually you see 25-26C. While the 3900X usually stays in low 30s' with the same water cooling set up.

This 3900X is my first AMD CPU. Got it last September. I just assume this is how it works. Until I build another PC with a 3600 last week for a friend. The 3600 actually idles a little higher at ~38C with a 240mm AIO. I don't think radiator size will affect idle temperature that much. It is just that particular chip has a higher idle temp. Both chips do take longer than Intel CPUs to cool down after a heavy work load. But not as long as 20 second like yours.

 

Regarding to power draw. Could be some settings in the BIOS. My 3900X will pull ~190w if the PBO is on and the power limit removed.