Worth Lapping?

[Bearded1]

Hi all. Bought a new hsf (Raijintek Tisis) and before fitting i noticed that the base is visibly convex to the extent that when set rocking from side to side on the desk it takes 5-6 secs to stop. When running IBT core temps peak in the low to mid 80s. BOINC running at 100% peaks in the 68-70 region. I have tried remounting several times. Apart from the first time temps have been consistent across mounts. This is an i5 4590k @ 4.6Ghz 1.31v. Considering that all the reviews i looked at rate it as being within 2-3 deg of the top end coolers such as Noctua NH-D14 it just seems like 80+ is a bit hot. What sort of temps should i expect at that sort of speed/volts? I know that lapping won't give me a huge drop in temps but surely just making the base flat would help. The cpu has already been lapped so is completely flat.

 

[frogspawn]

OK perhaps i can help here.

The reason why its rocking and as you quite rightly pointed out the TSIS is convex for a reason is that CPU IHS's are in general CONCAVE. So concave plus convex = good connection. But since you have already lapped your cpu then indeed you would find the issue you described.

My advice lap the tsis sink also to create a completely flat connection.

Good luck buddy

 

[Bearmann]

I have not heard that CPU's are concave. Regardless, most of the better heatsinks today are convex to improve contact in the center. I don't think that I would mess with it, that is, lap it.

 

[Blain]

Hi all. Bought a new hsf (Raijintek Tisis) and before fitting i noticed that the base is visibly convex to the extent that when set rocking from side to side on the desk it takes 5-6 secs to stop.

If it's that bad, get to lapping.

 

[Bearded1]

I'm tempted to lap anyway just cos i'm one of those people who likes tinkering but i guess what i'm really asking is are those temps normal for that sort of speed/volts with what is a high end air cooler. Forgot to mention room temp is about 16-17 and case is running with an open side atm cos i sort of forgot to measure to see if it'd fit.

 

[MrTeal]

I have not heard that CPU's are concave. Regardless, most of the better heatsinks today are convex to improve contact in the center. I don't think that I would mess with it, that is, lap it.

The IHS on a CPU can become concave after you've used a convex cooler with a lot of mounting force. There was a bit of controversy a few years ago during CPU cooler testing where flat bottomed coolers were doing poorly on reviewer's test beds after convex ones had been used and deformed the CPU.

 

[Bearded1]

Well i found the problem. Removed the cooler to try remounting again and noticed a gap between the cpu plate and the centre 3 heatpipes. Using a skinny piece of paper i discovered the gap goes 2/3 (27mm!) of the way across the width of the base. So the only proper contact between heatpipes and base is on the outer 2. Which because of the aforementioned convex issue weren't making good contact with the cpu. Grrrrr.
Still, glad i noticed that BEFORE i lapped.

 

[Ken g6]

If you can only fit a skinny piece of paper into the gap, shouldn't your TIM fill it in? You are using TIM, aren't you?

 

[Techhog]

If you can only fit a skinny piece of paper into the gap, shouldn't your TIM fill it in? You are using TIM, aren't you?

It would be hilarious if someone who laps their CPU doesn't know to use TIM. Also very sad.