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Windows 7: Extremely wierd DPC latency issue

09 Jun 2011   #1

Extremely wierd DPC latency issue

I didn't know if i should have put this in hardware, but i decided this would be fitting.

I'm not trying to stroke the e-peen, but i know what i'm talking about, so any advice i'll comprehend.

I noticed after a recent reinstall to throw on 64bit when my cpu was under a respectable amount of load i would stutter, like if my dpc latency was high (video and audio stuttering). I decided to download a dpc monitor - averaging around ~2000us. I disabled pretty much every single piece of hardware in device manager besides my gpu (too lazy to restart and toss my cable in the onboard, plus if it's my gpu i don't wanna know and i doubt it is) and no luck. After frantically looking for a solution, i found a tool called latencymon. Essentially, it tells you what driver is causing the most latency, so you can identify a bad driver with a bad piece of hardware or just a bad driver. Excited, i run the program and to my suprise - my latency does not peak 300. I ran the other monitor to see if it was just bugged - it did not peak 300. When i turn off latencymon, my latency goes right back up.

Although i can just run latencymon and call it a suitable band-aid (it's what i've been doing) it DOES eat up a significant amount of resources (~100-200mb of ram, 25% of my cpu) and is annoying to keep running in the back.

So, i was wondering if anyone could tell me what does that program actually do that it's somehow rectifying my problem? Or what IS the source of my problem?

Thanks in advance.

EDIT: Forgot my specs, but probably unhelpful since hardware doesn't seem to be the problem.. (which doesn't make sense as it is)

Asus/megatrend (i believe) VIOLA mobo (good luck finding it)

Nvidia GTX 260

PhenomX4 920 @2.8ghz (am2+ mobo)

5GB DDR2 ram

USB sound card

My System SpecsSystem Spec
09 Jun 2011   #2

Win 8 Release candidate 8400

there are more then 10 Latencymons. witch are you using?
My System SpecsSystem Spec
09 Jun 2011   #3
Microsoft MVP

Vista, Windows7, Mint Mate, Zorin, Windows 8

This is at best mysterious. Usually there are drivers that cause the problem. I have no direct answer for your problem, but here is an additional latency checker which may be good to run and a thread that helps in debugging such problems.

DPC Latency Checker
How to get the cause of high CPU usage by DPC / Interrupt - MSFN Forum
My System SpecsSystem Spec

09 Jun 2011   #4


Resplendence Software - LatencyMon: DPC, ISR and pagefault execution monitor

That fixes the problem. I use DPC Latency Checker to determine my actual DPC latency.

Gonna try updating my chipset drivers now too, i should have done that awhile ago but kind of assumed since i just reformatted that it would autoupdate.

EDIT: No luck, still high latency. Latencymon still fixes it.

May i add, when running latencymon the latency averages at the ~250 us range, which is still high.
My System SpecsSystem Spec

 Extremely wierd DPC latency issue

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