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184 Posts

05-02-2011

United States of America

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Re: T420S Display Switching To 50Hz On Battery Power

2011-06-08, 13:54 PM

Thanks JameZ, that clarifies why I was lucky enough for not seing refrash rate drop to 50Hz.

Thinkpad W520, 2720QM, Crucial SSD M4
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3538 Posts

07-12-2010

Malaysia

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Re: T420S Display Switching To 50Hz On Battery Power

2011-06-21, 8:18 AM

@All,

I've written up 2 KBs on this issue on how to modify the inf files to prevent the refresh rate to change when AC is unplugged.

I've provided these steps as development will not be releasing any drivers to fix this issue instead requesting those who wants to prevent the refresh rate change to do a modify inf instead.

T420s steps here
http://forum.lenovo.com/t5/T400-T500-and-newer-T-series/T420s-Screen-refresh-rate-drop-to-50Hz-when-on-Battery/ta-p/461845

T400 steps here
http://forum.lenovo.com/t5/T400-T500-and-newer-T-series/T400-Screen-refresh-rate-drop-to-50Hz-when-on-Battery-Intel/ta-p/461797

 

If you are having issues after installing the modified inf driver, please post it here.

 

//JameZ

0 person found this solution to be helpful.

This helped me too

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207 Posts

08-28-2008

Israel

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Re: T420S Display Switching To 50Hz On Battery Power

2011-06-21, 8:56 AM

I have T420s.

Driver version: 8.15.10.2342

No kit32889.inf, only kit33533.inf, found in path: C:\DRIVERS\WIN\VIDEO\INTEL\Graphics\Graphics.

 

BTW, there are 2 places in kit33533.inf file that have 0XF900 value:

 

 

[PwrCons_ILK_AddSwSettings]
HKR,, FeatureTestControl,%REG_DWORD%, 0xF900 ;


[PwrCons_SNB_AddSwSettings]
HKR,, FeatureTestControl,%REG_DWORD%, 0xF900 
HKR,, RsDisableDeepRC6,%REG_DWORD%, 1

 

 Need instructions on how to procced.

___________________________________________________________
Lenovo Thinkpad T420s
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23 Posts

05-21-2011

Germany

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  • Message 64 of 87

Re: T420S Display Switching To 50Hz On Battery Power

2011-06-21, 10:17 AM

What about people like me having this same problem on an x220 IPS?

 

btw: great that there will be no driver fix :-( 

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34 Posts

04-27-2011

San Francisco, CA

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  • Message 65 of 87

Re: T420S Display Switching To 50Hz On Battery Power

2011-06-21, 14:45 PM
Thanks for the fix. Haven't tried it yet, but will report back on how it works. IMHO, however, it would be better if the driver that Lenovo provides had this modification already built in. This way we wouldn't have to manually fiddle with things every time we updated the drivers. For example, I know Toshiba has this pre-applied to the drivers it released for its R series.
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3538 Posts

07-12-2010

Malaysia

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Re: T420S Display Switching To 50Hz On Battery Power

2011-06-21, 16:22 PM

@Roy,

Change value of 0xF900 to 0xF940.

 

@olidie,

 

Is it the X220 IPS screen ghost issue that you are having?

 

//JameZ

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207 Posts

08-28-2008

Israel

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Re: T420S Display Switching To 50Hz On Battery Power

2011-06-21, 16:24 PM

Change in both places?

Edit: changed in both places, it works!

___________________________________________________________
Lenovo Thinkpad T420s
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48 Posts

05-31-2011

Huntersville, NC

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  • Message 68 of 87

Re: T420S Display Switching To 50Hz On Battery Power

2011-06-21, 16:30 PM

What about the W520?

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3538 Posts

07-12-2010

Malaysia

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Re: T420S Display Switching To 50Hz On Battery Power

2011-06-21, 16:50 PM
@chickenleg0413,

Its the same for the W520 as well.

//JameZ
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13 Posts

04-11-2011

United States

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  • Message 70 of 87

Re: T420S Display Switching To 50Hz On Battery Power

2011-06-21, 19:10 PM

Just applied this fix to my T400.  Confirmed, it works.  Now if Lenovo can just solve the T400 dithering problem, the laptop will finally be at its full potential. :)

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