Thermal sensor dieing or something else?

[Armadillo]

My 2nd machine uses my old 5850 & while it's working fine the temperatures seem odd.

Basically, it idles at about 50C. The very instant you open a game, the temp instantly jumps to around 67C, then makes another instant jump to 95C or so.The second you stop using 3d clocks, it pretty much instantly drops again.

It never used to do it, it used to make a slow gradual climb and slowly cool down as expected.

When it's apparently 90C+, I've had the side panel off and the card does not feel that hot.

Can a temp sensor just give up and die? or something else at play. Thermal paste has never been changed, could that cause it, I would have thought you would still have a gradual climb though.

Fan is working and games are fine, no throttling or artifacts, but then I'm not sure when a 5850 would start to throttle anyway.

Thanks.

 

[yoinkF]

It's worth whipping the cooler off and changing the thermal paste, it could be that it has dried up completely and isn't allowing for efficient heat transfer between the die and heatsink. It would cause it to behave in the exact same way you're describing if it has dried up and become useless. It's not impossible for the temperature sensor to fail of course, it's just less likely for it to be that rather than a simple thermal paste issue!

 

[Armadillo]

Thanks. I'll change out the paste then, see how it goes.

Quick edit because I don't want to double post.

Thermal paste must have been on it's death bed. Before changing. Idle 50C, instantly spiking to 67C, then 90+. Fresh mx4 on there. Idle 28C, gaming 53C. Gradual climb, no spike.

Always thought when thermal paste went bad, temps would just be higher. Didn't think it would spike like that.

 

[V F]

Was it white and powdery when you took it off?

 

[Armadillo]

Was it white and powdery when you took it off?

It was still grey, but it was hard and came off in chunks when I wiped it away.

 

[mattyfez]

Thanks. I'll change out the paste then, see how it goes.

Quick edit because I don't want to double post.

Thermal paste must have been on it's death bed. Before changing. Idle 50C, instantly spiking to 67C, then 90+. Fresh mx4 on there. Idle 28C, gaming 53C. Gradual climb, no spike.

Always thought when thermal paste went bad, temps would just be higher. Didn't think it would spike like that.

I suppose it would depend on the particular material used, I'm sure there are quite a few different compositions, some look like toothpaste, some grey, some metallic etc, so I guess they would degrade differently with different characteristics.

 

[V F]

I decided to strip down my XFX 5870 Black Edition last night after some curiosity. That and for many years it was always loud and quite hot. Idle was always 44c and load 78c.

I was surprised to see a clear sticky plastic cut out square on the copper plate that the GPU core slipped between? Don't see how. Took it off as there was lots of dried paste all over and around it. Smoothed off the copper contact and used some old Shin Etsu. Think it was X23-7783D. They recommend putting it in a glass of hot water for several minutes as the stuff feels quite dry. Nice and gooey after that. Idle temperature dropped to 37/38c and load 65/66c. Tiny fan on this card though.

 

[nashathedog]

It was still grey, but it was hard and came off in chunks when I wiped it away.

How's it performing now?

I decided to strip down my XFX 5870 Black Edition last night after some curiosity. That and for many years it was always loud and quite hot. Idle was always 44c and load 78c.

I was surprised to see a clear sticky plastic cut out square on the copper plate that the GPU core slipped between? Don't see how. Took it off as there was lots of dried paste all over and around it. Smoothed off the copper contact and used some old Shin Etsu. Think it was X23-7783D. They recommend putting it in a glass of hot water for several minutes as the stuff feels quite dry. Nice and gooey after that. Idle temperature dropped to 37/38c and load 65/66c. Tiny fan on this card though.

I bet you wish you's done that years ago now, I've seen a few pic's on the net where people have taken a card apart and found lumps of plastic partially covering where the paste should be, A few years ago I had an MSI TFIV 290x Gaming which went straight to 94 degrees underload, even a 100% fan speed struggled to take a few degrees off and when I saw some pics like mentioned I pulled that apart in the hope it was a similar issue, no such luck though, I put some quality paste on it and managed to get it down by a few degrees but it still sat at 90 degrees under load with a 90% fan speed.

 

[V F]

Heh, yeah. I really should have done it once the warranty expired. Though I'll be replacing these cards soon anyway but was still curious to see. The question is though, what the heck was a sticky plastic cover doing there to begin with? It was nearly buried in paste and what paste there was, was covered over the die transitors. It was so messy.

I remember in the past with browser acceleration, simple scrolling the browser would ramp the fan up and down. Sometimes reaching 50c. Now browsing the temperature only goes up to 40 - 43c depending on what it is but there is no change in fan levels which is quiet. Even with one 120mm rear fan running at 540rpm while keeping the rest off.

I still don't understand why that sticky plastic was there. It was quite hard to get it off since it was so sticky due to the heat no doubt and it was holding the heat. If anything once it was all cleaned and checked it with a torch, it wasn't quite fully making contact since the plastic sat on the silver ridge of the chip on the PCB. As there was a slight wobble without the paste. Once it was off no wobble with no paste.