C940-14iiL

Discussion in 'Lenovo (IBM)' started by kurt corbin, Nov 21, 2019.

  1. lovelaptops

    lovelaptops My friends call me Jeff Senior Member

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    Excellent points Kurt. I've never experienced a migraine of any kind, but I would steer clear of any display that risks causing one if you know you are susceptible. I do think the fan issue is easily curable, in time. Not so sure about jitters. Light bleed has never bothered me in actual use. Good luck.
     
  2. kurt corbin

    kurt corbin Scribbler - Standard Member

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    Yes. The Yoga C930's have only Kaby R. Some of them may have been benchmarked without having had firmware and software installations that give some protection from the Spectre family of viruses, but reviewers are unlikely to mention this, or even know about it. These installations diminish performance significantly. Ice Lake has hardware-level protection, which diminishes performance less and is more effective. I can't believe there still hasn't been a Spectre attack.

    I guess we have to wait for Lisa's review to see what's up with the digitizer. I hope she gets the 3840p, which, by the way, is 500 nit, up from the 300-nit C930.

    Here's the C930 thread.
     
    Last edited: Dec 1, 2019
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  3. desertlap

    desertlap Scribbler - Standard Member Senior Member

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    So a couple of points.
    1. Burn-in TBD on the on the display used in HP. It's a Samsung panel which gives me hope.

    FWIW, generally speaking the issue with "burn in" has for all intents and purpose been mitigated for most use cases within the last a couple of generations of OLED that you are likely to see in a laptop or tablet. I'd say 99% of the reports of burn in come either from older generation televisions or phones.

    To give one admittedly anecdotal data point. We have a handful of customers using GB2s or Samsung Tab S4 devices in conjunction with our custom devices. In those cases they are on pretty much 8-12 hours at a go with a fairly static display (the middle section changes but the overall UI stays consistent). We haven't seen any issues with burn in or other artifacting with either unit.

    TLDR: Given that the HP OLED is a Samsung panel and is in fact a slightly newer gen of the panels used in those two devices, I'd say its a non issue. of course YMMV. And also the Spectre is available with a conventional LCD panel albeit 1080p.

    So as to PWM, it's pretty straight forward at this point. If it's OLED, it will use PWM to regulate brightness. There is some tech on the medium horizon that will hopefully change that, but not soon.

    OTOH, We are hearing that Samsung might announce mobile and laptop displays based on their QLED tech as soon as CES2020. QLED has some of the benefits of OLED such as better colors and faster response time. And with QLED companies have a much wider range of backlight options.
     
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  4. kurt corbin

    kurt corbin Scribbler - Standard Member

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  5. desertlap

    desertlap Scribbler - Standard Member Senior Member

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    From what we have been told the Razer is an unusual exception with a custom controller that does some unique tricks. It still "pulses" the display, but does it more dynamically and non-linearly e.g. different portions get dimmed while the whole display doesn't necessarily.

    It's somewhat like local dimming with conventional LED backlit displays.
    Additionally it's supposedly not very power efficient and has gray scale linearity issues. Of course we haven't tested it ourselves since that type of system is not something our customer base would use so the information we have is what we've been told.

    EDIT: For the record, the display in the HP does use PWM
     
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  6. kurt corbin

    kurt corbin Scribbler - Standard Member

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    So if you have an oscilloscope, why not see what's up with the HP's PWM? You'd be the first to publish that, as far as I can tell.
     
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  7. lovelaptops

    lovelaptops My friends call me Jeff Senior Member

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    Excellent posts by both @kurt corbin and @desertlap! Curious, any idea what % of people suffer effects from PWM? I've had devices with and without it and have never observed reactions. Presently, I'd be pretty concerned about the c940's apparent thermal problems, as documented by @kurt corbin, though I can't imagine they aren't easily fixed by updates. Thoughts?
     
  8. desertlap

    desertlap Scribbler - Standard Member Senior Member

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    @kurt corbin Not sure of what you are getting at here. I get that you are sensitive to PWM, but it's not something we normally test for. For us it's far more important that the various data interfaces (USB, Thunderbolt, Bluetooth, WiFi) perform to spec and secondarily that the display is reasonably color accurate (or can be made that way with calibration).

    Th reason I'm saying the OLED on the HP uses PWM is because that's what HP told us and I don't have any reason to doubt it.

    The sample we tested has gone back to the customer and my wife is using her system so I'm disinclined to take it from her to test for this.

    And FWIW, I have no interest in "being first" on something like this. It's not why I read and post here and isn't relevant to my job.
     
    Last edited: Dec 2, 2019
  9. kurt corbin

    kurt corbin Scribbler - Standard Member

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    Well, of course you know that it's all about the frequency. Did they tell you the frequency?
     
  10. kurt corbin

    kurt corbin Scribbler - Standard Member

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    Here ya go.

    About the thermal or fan problems with the C940. It's not clear whether those people have the 14" or the 15."
     
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