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ganon11000
Serial Port
Posts: 27
Registered: ‎06-28-2013
Location: United Kingdom
Views: 846
Message 1 of 11

T420 VERY bad DPC latency

I get DPC latency when any network activity is present. This includes WiFi and Ethernet.

 

I ordered recovery disks in hope that they would fix it but after reinstalling there is no luck.

 

I also installed driver-less / clean windows also to no luck.

 

This is the type of latency I'm getting:

http://imgur.com/Yv3lZGT

Guru
Posts: 9,598
Registered: ‎12-26-2009
Location: CA
Views: 810
Message 2 of 11

Re: T420 VERY bad DPC latency

Try this:

Grab TCPoptimizer from here: http://www.speedguide.net/downloads.php

Disable TCP Chimney Offload and Checksum Offloading, and reboot. Do this for both network adapters.

W520: 2960XM, Q2000M @ 1091/1380, 32GB RAM, 500GB&750GB HDD & 500GB SSD, FHD&MB168B+
X61T: L7500, 4GB RAM, 500GB HDD, XGA screen, Ultrabase
W550s: 5600U, K620M at 1164/1281, 16GB RAM, 512GB SSD, 3K touchscreen
X200s: SL9400, 6GB RAM, 64GB SD card, WXGA+ screen
TPT1: 1839-23U
ganon11000
Serial Port
Posts: 27
Registered: ‎06-28-2013
Location: United Kingdom
Views: 798
Message 3 of 11

Re: T420 VERY bad DPC latency

Sadly still no luck Smiley Sad

 

This is a DPC screenshot of idle and speedtest:

 

http://imgur.com/a/P4o5n

Guru
Posts: 9,598
Registered: ‎12-26-2009
Location: CA
Views: 784
Message 4 of 11

Re: T420 VERY bad DPC latency

Latest drivers? Maybe try disabling NetDMA and DCA too?

W520: 2960XM, Q2000M @ 1091/1380, 32GB RAM, 500GB&750GB HDD & 500GB SSD, FHD&MB168B+
X61T: L7500, 4GB RAM, 500GB HDD, XGA screen, Ultrabase
W550s: 5600U, K620M at 1164/1281, 16GB RAM, 512GB SSD, 3K touchscreen
X200s: SL9400, 6GB RAM, 64GB SD card, WXGA+ screen
TPT1: 1839-23U
ganon11000
Serial Port
Posts: 27
Registered: ‎06-28-2013
Location: United Kingdom
Views: 758
Message 5 of 11

Re: T420 VERY bad DPC latency

Still awful (mouse stuttering etc..)

 

http://imgur.com/HGWnblu

ganon11000
Serial Port
Posts: 27
Registered: ‎06-28-2013
Location: United Kingdom
Views: 721
Message 6 of 11

Re: T420 VERY bad DPC latency

GOOD NEWS!!

 

I fixed the ethernet - I cleaned all the sockets and connecters internally and removed the WiFi card and this is ethernet http://imgur.com/Euk1NXD Smiley Happy

 

Bad news is the wifi card must be bad if it makes that much DPC. What WiFi card would you recommened? (Under £15 on eBay UK).

 

EDIT: Is this one any good? http://www.ebay.co.uk/itm/Lenovo-ThinkPad-X220-T420-T520-W520-E520-X120E-WiFi-card-b-g-n-Wireless-60... (I'm sick of intel cards DPC latency)

Guru
Posts: 9,598
Registered: ‎12-26-2009
Location: CA
Views: 704
Message 7 of 11

Re: T420 VERY bad DPC latency

I'm not sure then. I get similar DPC latencies under high wifi load too. No mouse stuttering or hiccups in audio playback though.

You'll run into a problem using generic cards because of a BIOS whilelist for wireless broadcasting devices; your system won't boot with an unauthorized card. Workarounds exist, though.

W520: 2960XM, Q2000M @ 1091/1380, 32GB RAM, 500GB&750GB HDD & 500GB SSD, FHD&MB168B+
X61T: L7500, 4GB RAM, 500GB HDD, XGA screen, Ultrabase
W550s: 5600U, K620M at 1164/1281, 16GB RAM, 512GB SSD, 3K touchscreen
X200s: SL9400, 6GB RAM, 64GB SD card, WXGA+ screen
TPT1: 1839-23U
ganon11000
Serial Port
Posts: 27
Registered: ‎06-28-2013
Location: United Kingdom
Views: 696
Message 8 of 11

Re: T420 VERY bad DPC latency

Whaty cards are on the whitelist?

Guru
Posts: 9,598
Registered: ‎12-26-2009
Location: CA
Views: 676
Message 9 of 11

Re: T420 VERY bad DPC latency

They'd be the ones that shipped with the T420 machines. More annoyingly, they also have to be Lenovo branded ones.

W520: 2960XM, Q2000M @ 1091/1380, 32GB RAM, 500GB&750GB HDD & 500GB SSD, FHD&MB168B+
X61T: L7500, 4GB RAM, 500GB HDD, XGA screen, Ultrabase
W550s: 5600U, K620M at 1164/1281, 16GB RAM, 512GB SSD, 3K touchscreen
X200s: SL9400, 6GB RAM, 64GB SD card, WXGA+ screen
TPT1: 1839-23U
ganon11000
Serial Port
Posts: 27
Registered: ‎06-28-2013
Location: United Kingdom
Views: 651
Message 10 of 11

Re: T420 VERY bad DPC latency

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