Thinkpads Forum

I am having very severe issues with DPC latency on my T400. When playing music with iTunes and loading webpages, THIS is what happens.

Whenever the bar spikes up to the "red" levels I experience a dropout in whatever audio is playing. I have tried disabling devices in Device Manager which did not help. Turning off the hardware switch for wireless helped slightly, as I couldn't load any more pages. This tells me that it must be a combination of the Intel wireless adapter and something else.

Does anyone have experience with this, or have a solution to offer?

UPDATE: I let it run while typing this out and the red bars are through the roof! Absolutely maxed out the charts. This is unbelievable. I know T400's have issues with latency, but I haven't heard of anything this bad!

This is for a Dell, with nVidia, and broadcom wireless... but the testing method is sound ... give it a read through...

http://www.scottmetoyer.com/archives/my ... pc-latency

Might help you find the culprit

Thanks for that. I was right in guessing it was something to do with the WLAN, as NDIS.sys and tcpip.sys are right at the top. Here is the outputted chart:



I also see ACPI.sys, something to do with power management perhaps? Seeing USBPORT.sys I unplugged everything from the USB ports and tried again, to no avail. Hopefully someone else can offer some input on this.

At least for the guy's broadcom there was a "hacked" driver... have you tried other revisions(even older) of the intel driver either/both from IBM or striaght from Intel?

I know when it comes to nVidia video drivers, I have in the past opted for an older one for some situations (stability/speed in certain games).

Wat. Never had DPC issues that bad with the T400 (barring Windows 7 beta/RC), and even with occasional bars in the 3000us, the audio doesn't drop out noticeably.

What's your wifi driver version?

Might also want to try LatencyMon to watch the DPC and ISR counts in real-time.

Also remember to set RMClock to the maximum multiplier during latency queries. SpeedStep adds inaccuracies to the readouts.

EDIT:
http://s1119.photobucket.com/albums/k64 ... Latencies/
Two downloads at 10kb/s each (Internet here sucks), and Winamp playing FLAC files.
CPU locked to maximum multiplier.

Colonel O'Neill wrote:Also remember to set RMClock to the maximum multiplier during latency queries. SpeedStep adds inaccuracies to the readouts.

I think this was my problem. After switching it to maximal performance my latency went way down, and iTunes no longer completely cuts out. There is still a faint stutter somewhere in there though.

I let Windows handle the wireless driver, it's version is 13.0.0.107 dated 9/15/2009. I'm going to try and find a newer version and see if that helps.

LatencyMon comes up with way different readings than DPC Latency Checker. Here are my readings:

Drivers
http://imageshack.us/photo/my-images/808/drivers.png/

Report
http://imageshack.us/photo/my-images/694/reportvh.png/

Update: New wireless driver, version 13.5.0.6, dated 1/19/2011. It seemed to help quite a bit, more than halving the Highest DPC exception count. Here are some new screenshots:

Drivers
http://imageshack.us/photo/my-images/33/driversv.png/

Report
http://imageshack.us/photo/my-images/819/reportcu.png/

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OT: 10kb/s? Is that the norm over there or is it just your ISP?

I have 13.5.0.6 for the 5300... Not sure where I got it from anymore.
Also using 10.5.0.1026 for Intel Rapid Storage Technology...

Firewire port, ExpressCard controller, Intel Management Interface (under System devices) I've all disabled.

My internet has been ridiculously slow for no apparent reason today. And apparently 4mbps downlinks are as good as you can get here.

Where are you seeing RST in device manager? If it's the one under IDE ATA/ATAPI controllers then I have 8.9.2.1002 from Lenovo. The newest on Intel for RST is 10.1 something.

I skipped Matrix Storage and am using Rapid Storage drivers.

I found 10.5.0.1027 here, hopefully that's the one. I'm installing it now.

Blargh. Looks like I'm .0001 behind. Too lazy to update.

Colonel O'Neill wrote:Blargh. Looks like I'm .0001 behind. Too lazy to update.

You may not be. I installed the 1027 package and device manager reports 1026. I'll check the dpc later, out and about now.


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