6950s running hotter after thermal paste...wtf?

[AlexWaters]

I have two Sapphire 1GB 6950s, I have been running them for about a month - and getting the following consistent stats:

Card #1
Core Voltage: 1120mV
Core Clock: 920mhz
Memory Clock: 520mhz
Fan: 100%
Temperature: 78-79C

Card #2
Core Voltage: 1120mV
Core Clock: 920mhz
Memory Clock: 520mhz
Fan: 100%
Temperature: 76-77C

and getting 725 megahash total.

So I thought it would be a good idea to open up the cards and replace the thermal paste. In my experience, this normally lowers temperatures. Much to my dismay, card #1 is running 84C and card #2 I have been shutting off (stop mining) after it hits 86C - which takes 10 seconds to get there.

All of my stats and the specs are the same (except the temps/Mhash), I have checked them in both GPU-Z and MSI afterburner (what I use to OC).

I was suggested in IRC to try using zip ties because the heatsink does not sit well in these cards - I was shown this photo: http://imgur.com/TWF7Z

I tried that, but it hasn't changed anything.

The thermal paste I used is Artic Silver, and I have many years experience applying it evenly and in a thin coating. I have reapplied the paste 2 times (cleaning with alcohol wipes) to card #2 with no avail.

Any help would be really appreciated - this makes no sense to me!

Thanks!

[Tx2000]

Arctic Silver has a long set in time compared to other thermal pastes.  It can take hundreds of hours before it starts achieving it's best results.  Also, by the sound of your explanation, you are using a very old method of spreading the paste manually.  It has been found that that particular method isn't always best as it leaves room for error by manual spread (re: tiny bubbles/pockets).

Try reapplying by putting a small pea sized (emphasis on small pea, not "regular" pea sized) in the center of the core and allowing the natural pressure of the heatsink and mount compression to spread the thermal paste out.  Again, with arctic silver, it will take a long time before it reaches optimal.

[AlexWaters]

That sounds reasonable - but doesn't explain why one card is running so much hotter than the other - their idle temps are 10C apart...

[Jack of Diamonds]

I stopped applying AS5 because it takes so long to break in.
Would recommend IC Diamond 7. Not only does it have slightly better thermal conductivity properties (synthetic diamonds), it's effective immediately.

Sure it costs 3 times as much which is not a plus but these tubes last dozens of applications.

[Sannyasi]

That sounds reasonable - but doesn't explain why one card is running so much hotter than the other - their idle temps are 10C apart...

just plain unscrewing the heatsink and reseating it may help- as mentioned above, bubbles can form and the paste may for one reason or another end up on only part of the chip you're cooling. i've had two occasions with GPU's similar to this one with the paste not being properly distributed and the other is i missed a screw on the main bracket that mounts the cooler to the GPU- then i've also forgotten to re-plugin the fan a couple times but i assume you've checked that sort of noobishness......

[AlexWaters]

just plain unscrewing the heatsink and reseating it may help- as mentioned above, bubbles can form and the paste may for one reason or another end up on only part of the chip you're cooling. i've had two occasions with GPU's similar to this one with the paste not being properly distributed and the other is i missed a screw on the main bracket that mounts the cooler to the GPU- then i've also forgotten to re-plugin the fan a couple times but i assume you've checked that sort of noobishness......

I tried reseating 3-4 times with no luck. If it doesn't improve by this time tomorrow I may consider getting that better thermal grease that Jack is talking about.

I still don't see how the paste could be the problem though - maybe I should try sanding the heatsink to get it to conduct better? Anyone know of any other mods to get the heatsink to sit better on the die?

[erek]

i had the same problem with Arctic Silver Ceramique... my only solution was to use Arctic Cooling MX-4... just a drop on the core

[AlexWaters]

i had the same problem with Arctic Silver Ceramique... my only solution was to use Arctic Cooling MX-4... just a drop on the core

On graphics cards? Which card? 6950's? This is so frustrating =(

I have to tone back my hash rate on the hot card from 362 to 165. 

[computerparts]

You have years of experience applying the wrong way apparently. As was said before, the dot method is the proper way. Keep in mind a gpu is not the same as a cpu.

[AlexWaters]

You have years of experience applying the wrong way apparently. As was said before, the dot method is the proper way. Keep in mind a gpu is not the same as a cpu.

I've taking note of these new practices - and will try "tinting" and just applying a pea. Thank you for the reminder.

Although, I wouldn't call it "the wrong way" if it's what worked 15 years ago, they have just improved upon an old practice... and I was unaware of this improvement.

What do you mean when you say that a GPU is not the same as a CPU? Are there according methods for application of the thermal paste?

[AlexWaters]

I just finished re-doing the thermal paste with ceramique - this time using the tint and bead method. Surprisingly, the temps now idle at the same 51C - so it is clear to me that this is definitely a thermal conductivity issue.

The problem is that now both cards are above 80C at full load. I'll wait 24 hours to see if this improves, but I went ahead and ordered the MX4 to see if that helps. Likewise, I will keep this thread updated for anyone down the road experiencing similar issues.

I'm considering going down the watercooling route - as this might be cost-effective in the long run (if I end up with 4 6990s, so I don't need a box fan 24/7).

I was looking at the mcw60 block, I can get two of them for around $30 each. Does anyone know of a cheaper alternative to these blocks? Or a resource for watercooling GPUs?

Thanks for all the help guys, I was freaking out that card #1 was somehow damaged - and it looks like that's not the case.


Also, is mineral oil submersion an option?

[AlexWaters]

Ok so I have the temps back to where they should be. What a relief!

It seems that the heatsinks do not sit flush on the dies - and I had to use twice the normal amount of ceramique to get proper thermal conduction. It's still not where I want it to be, but maybe the MX4 will change that.

Thanks for all the help, anyone recommend lapping the HS?

[Jazkal]

How long did it taje the ceramique to settle down to working temps? What was the eventual drop in temp?

[AlexWaters]

I have them running at 78/79C and the temp hasn't settled down much in ~15 hours. Fortunately, they're pretty close in Mhash to when I started - which is better than 2 days ago.

[xtoro]

You should also do some heat cycling as well for it to settle properly before overclocking at high temps.

Apply paste, re-assemble and run at moderate temps (40-65ish *C, no higher!) for about 24 hours.  Shut it down and let it cool off completely for about an hour.  Fire up again, at least 2 hours, another hour cooldown.  You should do the heat and cool cycle at least 4-5 times.  This will help get to your break in period faster and you'll see cooler temps in the end.  If you just let it run super hot right after you apply it, it won't do very well, ever.

After your cycles, crank the clocks and report your new temps

[marvinmartian]

I'm tellin' ya.  Those cards are nothing but a pain in the neck.

[Jazkal]

I've read all this, and decided never to use Arctic Silver, I'll be getting some 'IC Diamond' instead (no set time required).

[CydeWeys]

Those are some high temps considering fan speeds are at 100%.  Have you tried running with the side off the case off and a box fan pointed in?

[nebiki]

I'm tellin' ya.  Those cards are nothing but a pain in the neck.

no, man. best resale value after bitcoin dies. and best option to use as a gaming card.

You have years of experience applying the wrong way apparently. As was said before, the dot method is the proper way. Keep in mind a gpu is not the same as a cpu.

i've been doing it this way for years, too. never had any problems. i don't really see the difference between cpu cooling and gpu cooling, either. less pressure?

Those are some high temps considering fan speeds are at 100%.  Have you tried running with the side off the case off and a box fan pointed in?

i don't think it's a dedicated mining rig, so i'd rather try to get some airflow going inside the case. probably not enough fans blowing in (i've had my case fans running depending on cpu temperature before i've started mining. basically they were not blowing any air at all, which resulted in about 15K higher temperatures).

i can't stress enough that going for LIQUID COOLING is the proper way for gamers who casually mine with their rigs (or anyone who has their rigs in their room). sitting/sleeping next to a 1000dB machine won't exactly increase your standard of living. the 10 bucks a day you make off mining won't make up for that.