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markusj
Posts: 3
Registered: ‎05-04-2012
Location: Germany
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[T520 + Mini Dock Series 3] NVidia GPU throttled while running docked without battery?

Hi,

 

i had been a bit disappointed by the performance offered of the dedicated GPU/NVidia Optimus. By accident i discovered, the GPU provides MUCH more performance if a battery is plugged in!

 

Let me describe my setup:

Thinkpad T520 with a Quadro 4200M (NVidia Optimus setup) and a default 55+ battery, which i normally unplug while on dock. (Yes, the battery management is nice, but temperature increases the battery aging rate, too. My last laptop died before my batteries even reasonable weared out ..., however, back to topic).

Docked but WITHOUT battery, i get poor framerates of about less than 30 fps while running a rather simple game on 1024x768px with least possible quality. High quality settings lead to about 10-15 fps.

Now the interesting part: Docked and WITH battery, i get 120-130 fps by using the highest quality settings possible.

 

I discovered  this behaviour on each game/benchmark i ran, and noticed the same results, not depending on the battery state while booting (plugged/unplugged). In fact, it can even be observed if i  plug in the battery while running a game/benchmark, the fps increase instantly.

 

But things get even more interesting: If i do not use the dock and connect the AC power supply directly to the laptop itself, nothing described above happens! It just runs smooth and fast like desired, independent from the battery state.

 

So i am curious: If you own the same hardware setup like me (T520 with NVidia Optimus and Mini Dock Series 3 docking station), can you confirm this behaviour?

 

I can currently imagine three reasons:

1. The Mini Dock Series 3 can not provide the power required to run without throttling. (But then: why is it shipped with a 90W power supply?)

2. The BIOS/UEFI/Embedded controller simply has a bug

3. Ehm, yea, what i have not said until now: I am running Ubuntu Linux 11.10 x64 with Bumblebee 3.0 (see PS). So it is absolutely possible there is a bug in the way the kernel, bumblebee or something else talk to the hardware, and which gets triggered by the docking station. But to be honest: I do not really believe this, the behaviour looks to strange/systematic/hardware-driven for me.  But i simply can not preclude it.

 

Regards,

Markus

 

PS: Bumblebee is a project targeting for NVidia Optimus support for linux, since NVidia does not provide drivers which support the hybrid graphics approach. By version 3.0 a major rewrite has been done to increase stability and reliability. Ii really like it, it works fast and stable for me.

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ThorsHammer
Posts: 2,400
Registered: ‎04-08-2011
Location: USA
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Re: [T520 + Mini Dock Series 3] NVidia GPU throttled while running docked without battery?

Confirmed.  It's well known and was discussed often when these machines came out.

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markusj
Posts: 3
Registered: ‎05-04-2012
Location: Germany
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Re: [T520 + Mini Dock Series 3] NVidia GPU throttled while running docked without battery?

I have not found any information about this issue while searching, maybe i used the wrong keywords. Is there any official statement from Lenovo why they do not fix it?
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ColonelONeill
Posts: 6,581
Registered: ‎12-26-2009
Location: Toronto
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Re: [T520 + Mini Dock Series 3] NVidia GPU throttled while running docked without battery?

It's intentional. You'd probably need a 135W adapter to run the dock and the machine at full performance. The battery is needed to provide power when the power draw exceeds the capabilities of the adapter.
W520: i7-2720QM, Q2000M at 1090/695/1390, 22GB RAM, 500GB HDD, FHD screen
TPT1: 1839-23U, stock ICS
X61T: L7500, 3GB RAM, 500GB HDD, XGA screen, Ultrabase
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ThorsHammer
Posts: 2,400
Registered: ‎04-08-2011
Location: USA
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Re: [T520 + Mini Dock Series 3] NVidia GPU throttled while running docked without battery?

The issue isn't really associated with the dock. 

 

You will find the issue reported most often by people testing performance and throttling while on AC, but with the battery removed. 

 

I don't know how to tell you to search for it, but it's definitely in the monster W520 throttling threads.

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markusj
Posts: 3
Registered: ‎05-04-2012
Location: Germany
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Re: [T520 + Mini Dock Series 3] NVidia GPU throttled while running docked without battery?

Well, for met it is associated with the dock. If i'm running directly on AC without battery and without dock, no throttling occurs. Therefore, the answer given by ColonelONeill appears to be plausible for me. I knew the W5x0 laptops are throttled (for a good reason) while running on a 90W power supply instead of the big 135W one, but had not expected this for the T5x0 models, too. I'm just thinking about buying a 135W power supply if i get a good deal at eBay. Has anyone tested if the bigger supply really "fixes" this issue? And by the way: What would the W5x0 guys do? There is not supply >135W, so they are forced to keep their battery plugged in, aren't they?
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ThorsHammer
Posts: 2,400
Registered: ‎04-08-2011
Location: USA
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Re: [T520 + Mini Dock Series 3] NVidia GPU throttled while running docked without battery?


markusj wrote:
Well, for met it is associated with the dock. If i'm running directly on AC without battery and without dock, no throttling occurs. Therefore, the answer given by ColonelONeill appears to be plausible for me. I knew the W5x0 laptops are throttled (for a good reason) while running on a 90W power supply instead of the big 135W one, but had not expected this for the T5x0 models, too. I'm just thinking about buying a 135W power supply if i get a good deal at eBay. Has anyone tested if the bigger supply really "fixes" this issue? And by the way: What would the W5x0 guys do? There is not supply >135W, so they are forced to keep their battery plugged in, aren't they?

I assumed you were running with a 135W or 170W power supply.