XPS 15 9550 temperature observations (undervolt + repaste)

Discussion in 'Dell XPS and Studio XPS' started by custom90gt, Dec 28, 2015.

  1. GoNz0

    GoNz0 Laptop Engineer & Online games hosting.

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    try it and let us know :)
     
  2. custom90gt

    custom90gt Doc Mod Super Moderator

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    The thermal pads are 1mm thick.
     
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  3. pressing

    pressing Notebook Deity

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    custom90gt, GonZ0 and Brian Anderson- I really appreaciate your help and thank you for taking the time to document your VRM efforts here.

    Tonight I took a stab at cooling the VRM.

    1. MOSFETS
    My thesis was that the MOSFETs are likely getting hotter than the R22 chokes; also heat is especially detrimental to performance of MOSFETs. Some roadblocks:

    A. Opening the laptop reminded me once again of the staggeringly small scale of parts; the AO chips are about 3mmx5mm and the TI chips are just a little larger.

    B. The distance from the MOSFETs to the bottom case looks to be approximately 5mm, stacking tiny pads which are taller than wide without any reasonable adhesive will be unstable. They will get quite inefficient at transferring heat when so thick and triple stacked

    C. The MOSFETs have related ultra tiny resistors next to them that I worry will not properly covered by the thermal pads and might effectively be isolated from any air cooling at all. Someone who is really careful with very fluffy thermal pads might be able to make that work but not me

    D. Given the tiny scale of the chips and the thick clay density of the Fujipoly 17 W/mK (which is all I have), making the pads too thick could, with a bit of pressure on the case bottom, knock a MOSFET off the board. I just don't have the tools to get the pad thickness just right

    2. CHOKES
    So now I understand why custom90gt decided to use thermal pads on the R2 chokes: they are relatively big, relatively robust, and close to the bottom case. Per custom90gt's recommendation, I tried 4 x 1mm pads and they all seemed to make good contact with the bottom case based on my distilled water test.

    3. TESTING
    I ran a few tests. On the "light" tests, the case got a bit warmer and performance improved a bit.

    Unfortunately, on more demanding tests (e.g. RealBench StressTest) things fell apart. The case bottom got really hot really fast, especially under the VRM area. After ~5 minutes:

    A. top of the keyboard (actually the plastic bar above the function keys and the carbon to the sides of the function keys) was hot but touchable. The heat was creeping down the keyboard after 10 minutes. You would not want that level of heat on the keyboard unless you lived in an igloo

    B. back few centimetres of metal bottom case (imagine below say the f4-f11 keys) was hot, almost too hot to touch

    C. most troubling was that the area on the bottom case between the fans and front of the rubber strip was incredibly hot, and I think that caused some real issues (GonZ0 described the death spiral when connecting the heat pipe to the case with thermal pads - heating up the case bottom such that the cooling fans were sucking in hot air, fighting a losing battle to cool the CPU & GPU. I could visualize that happening tonight)

    Never had these heat problems prior to padding the chokes tonight

    4. CONCLUSIONS
    A. Using less efficient thermal pads for the R2 chokes might provide a better balance, some extra cooling and performance without overheating the case as custom90gt documented

    B. High performance thermal pads for those running only light and medium intensity tasks could provide a small boost in performance when the VRM starts to heat up. However, with intense benchmarking and gaming, high-performance thermal pads on the four R2 chokes quickly overheated my case bottom, throttling the system towards 1Ghz. Also caused keyboard to get uncomfortably hot

    5. NEXT STEPS
    I removed the R2 choke thermal pads after a few hours of testing. Learned there is a lot of heat in the VRM department. Of course, will continue to think about this some more as there is some performance to unlock...
     
    Last edited: Sep 15, 2016
  4. GoNz0

    GoNz0 Laptop Engineer & Online games hosting.

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    I put some 1.5mm pads (the SSD one) on the offending parts around the VRM sensor and will be removing later today. Not enough gain and yet again I came to the conclusion this isn't a gaming laptop and will throttle when pushed as expected.
     
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  5. Ktulu85

    Ktulu85 Notebook Evangelist

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    Is it common for the fans to take a really long time to ramp down after heavy load such as gaming?

    My temps are decent while gaming and they fall back to respectable idle temps but the fans are still blowing at full speed for upwards of 20 minutes after the clocks and temps come down.

    Putting the computer to sleep obviously stops the fans and waking it up immediately after I have silent fans.

    Sent from my LG-D852 using Tapatalk
     
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  6. GoNz0

    GoNz0 Laptop Engineer & Online games hosting.

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    Yes it has to cool the board down as well so it will stay high until all sensors are back in range.
     
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  7. custom90gt

    custom90gt Doc Mod Super Moderator

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    Great report on your findings. I am surprised that for once my cheap thermal pads may be better than my Fujipoly ones (which were too thin for me to try on the chokes). I haven't had any problems with the laptop getting hotter than normal, and gaming for an hour didn't bother me either. I don't know how good of a test Rocket League was in comparison to say the Witcher 3 demand wise, but I experienced 0 throttling either CPU or GPU wise while playing it at 1080p. If I have some time i will try RealBench and see what happens.

    So far using the laptop every day at school (often in my lap while sitting in the comfy chairs at the library) I haven't had any issues with the chokes sinked. I'll probably leave it like this.
     
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  8. Ktulu85

    Ktulu85 Notebook Evangelist

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    Ok, thanks. I guess, I am coming from a huge gaming laptop that would have cooled a bit faster. So I was used to the fans stopping as soon as I closed the 3D application.

    I don't mind the noise, so as long as it keeps things cool, no worries!
     
  9. einsteinchen

    einsteinchen Notebook Geek

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    As it turned out, the system was undervolted for both test with the new thermal paste and pads. Apparently the changed voltage persists after turning TS off. I have now played again some Dota2 and recorded temps with HWInfo 64, this time I also report the VCORE, thus we can see if any undervolting is taking place.
    • green: new thermal compounds and undervolted
    • red: new thermal compounds
    [​IMG]

    Undervolting helps with temps and core clock, according to my two games of Dota2. Interesting is, that the VRAM (Ambient) shows a higher temp while keeping a higher clock speed.

    Undervolting did not change coil whine for me.
     
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  10. pressing

    pressing Notebook Deity

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    I thought ThrottleStop did the same to my laptop. It took me an hour of bumbling around to get that sorted but it has been rock solid since.

    1. I think the fix was completely uninstalling ThrottleStop then reinstalling; only had to do that once.

    2. If that does not work, I might have tried unistalling ThrottleStop, installing Intel XTU and running that for a few minutes, completely uninstalling XTU, then reinstalling ThrottleStop.

    FYI - So that you can see the status of ThrottleStop, on the options pane under "notification area" select show CPU/GPU/GHz in the bottom taskbar. I also have an octagon shaped indicator in the taskbar that is red when ThrottlStop runs and green when not running; I think that octagon appears automatically when ticking said items in the "notification area" of ThrottleStop but don't remember. Regardless, based on the MHz indicator I know when ThrottleStop is running (e.g. in idle CPU is at ~3.1GHz when ThrottleStop is on)
     
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