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Postby Kilou » Mon Feb 12, 2018 11:06 am

In the description of the Thinkpad T480, you mention that the video card is a Geforce MX150 but that the laptop does not use hybrid graphics (i.e. optimus technology). I'm unaware of any laptop using such a dedicated GPU without also having the Intel UHD620 integrated GPU, and thus having hybrid graphic. Could you please confirm if the T480 also uses optimus technology to switch between the integrated intel GPU and the MX150?

Also, do you know whether the WQHD display on the T480 uses PWM (pulse width modulation) to dim the diplay? If it does, do you know which frequency is used?

Postby The-ThoMas » Mon Feb 12, 2018 1:15 pm
Hi Kilou

At least in the standard Lenovo Spec they are mentioned as:
Intel HD Graphics 620 or Intel UHD Graphics 620 in processor only
Intel HD Graphics 620 or Intel UHD Graphics 620 in processor and NVIDIA GeForce MX150, 2GB GDDR5 memory;

http://psref.lenovo.com/syspool/TempFil ... 111734.pdf

I would say, it is highly unlikely, that Lenovo disables Optimus just for Neptun.

Regarding PWM, I have not found any info online. At least in the previous T470(s) line, PWM was only found in the touchscreen model: https://www.notebookcheck.net/Lenovo-Th ... 460.0.html

But as always, Simon will have the most reliable information on his hands ;)

Kind regards,
Postby Kilou » Mon Feb 12, 2018 2:34 pm
Thanks Thomas!
Postby simon-ses » Mon Feb 12, 2018 5:01 pm

We received the information concerning hybrid graphics from Lenovo, so it seems that the Intel UHD GPU is deactivated. We couldn't verify it yet with a real device and we will do so as soon as we can lay our hands on a t480. I will ask Lenovo about the wording from the PSREF. (In the short specs on notebookcheck.net the wording is "or": https://www.notebookcheck.net/ThinkPad- ... 172.0.html)

Concerning PWM we received mixed messages in the past (from all the manufacturers). I will ask Lenovo but I'm not 100% confident that we will get reliable information. Again it will probably be best to verify this with a demo device. (I'm not sure if we have the means to verify the frequency of the PWM, but if it uses low fequency PWM we should be able to verify this.)

Best regards,
Postby Kilou » Mon Feb 12, 2018 6:17 pm
Thanks Simon! It would be great if you could provide updates on these issues once you have a T480 in hands, hopefully soon during one of the Demo days. Thanks!
Postby The-ThoMas » Mon Feb 12, 2018 11:22 pm
The notebookcheck.net wording could be misleading, as they tend to list possible options (in the sense of: you can order it with Intel OR Nvidia GPU). The CPU i7-8550U supports Hybrid Graphics as well.

But we will see, I have ordered mine today ;)
Postby simon-ses » Thu Feb 15, 2018 10:52 am

I've got an answer concerning PWM with the T480:

"T480 use PWM brightness control, and frequency is 990Hz for both BIOS and Windows graphics"

The high frequency which is implemented should avoid issues that can be experienced by some users with LCDs using a low PWM frequency (100-300Hz)

Concerning the hybrid graphics we are still researching.

Postby Kilou » Thu Feb 15, 2018 10:46 pm
Thanks for the update Simon. Did you also get the information if PWM is used at all brightness levels or only below some threshold e.g. below 20% brightness? It seems Lenovo constantly change the display panels as last year's T470s WQHD display did not use PWM at all (according to notebookcheck.net).

Regarding hybrid graphics, it's probably a typo since the intel UHD 620 GPU is built into the CPU so it should definitely be a hybrid graphic setup with the MX150 and optimus technology.
Postby Kilou » Wed Feb 21, 2018 4:22 pm
regarding PWM, it seems the T480s with the same WQHD screen as the T480 has no PWM (https://www.notebookcheck.net/First-Imp ... 832.0.html). Does this mean the T480 uses a different dislay panel compared to the T480s?
Postby simon-ses » Wed Feb 21, 2018 9:25 pm
Here an Update concerning PWM range I received today:

This PWM is wide range PWM, so brightness control can control from 100% to nearly 1% by PWM control.

With the high PWM frequency this is what I would have expected.

The PWM information on notebookcheck cerning the T480s feels a little bit implizit, because non of the listed devices has an entry in that row. But I did ask Lenovo for PWM Information for the T480s WQHD panel.

Postby Kilou » Thu Mar 01, 2018 1:10 pm
In the T480, is it possible to disable the Nvidia GPU in the BIOS and run the laptop exclusively on Intel UHD620?
Postby simon-ses » Thu Mar 01, 2018 5:01 pm
The T480 does not support Optimus but uses a Windows feature to switch graphics. In the BIOS graphis aren't switchable (and for devices where it is (eg P51) it can only be set to the dedicated GPU only and it can't be selected to run with the Intel GPU only).
Postby Kilou » Thu Mar 01, 2018 5:31 pm
Thanks for the update Simon. That's strange since the MX150 supports Optimus according to the card specs (see https://www.geforce.com/hardware/notebo ... orce-mx150). If the T480 switches between the graphic cards with a Windows feature, than it likely won't work under Linux, which makes the T480 a no-go for me.
Postby simon-ses » Thu Mar 01, 2018 5:35 pm
Thats all I can tell you ..if you would have visited a DemoDay you could have looked at it yourself

Here the Ubuntu certification page for the T480 https://certification.ubuntu.com/hardware/201801-26056/

Here the disscussions on Reddit:
https://www.reddit.com/r/thinkpad/comme ... _and_cons/
https://www.reddit.com/r/thinkpad/comme ... ns_part_2/
https://www.reddit.com/r/thinkpad/comme ... core_cpus/

When we have some time we will give the new devices to the Alternative (https://thealternative.ch/) for testing and then we know more

ps.. we measured a battery life of 1050min for the T480 under windows
Postby Kilou » Thu Mar 01, 2018 5:59 pm
I went to the DemoDay last week in Geneva but the T480 was not there. Instead, they had a T470 which has no dGPU. But if Ubuntu certified the T480 with MX150 then I guess it should work somehow.
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