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DPC Latency - definite driver issue

Last response: in Windows 7
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July 9, 2011 9:39:57 AM

Hello all,

I'm trying to seek some help with a specific DPC Latency issue. The problem manifests with severe audio popping and slowdown with flash video stretched to fit my 1920x1200 monitor, and similar problems plus lowered framerates in 3D applications. Removing the Nvidia graphics driver removes the problem, but obviously that isn't a viable long term solution.

However, I don't think it's solely down to the GPU driver. The problem did not emerge immediately after a graphical driver update (I think it emerged after Windows Update installed updates), and driver versions make no difference, even if I roll all the way back to 1xx.x versions.

Using Latency mon, the main culprits are usually ataport.sys, ndis.sys, USBPORT.sys, or nvlddmkm.sys. HDAudBus.sys also ranks quite highly in execution time and DPC count. I'm 99% certain it's a specific conflict between my GPU and another device.

It's also important to note that there are NO DPC issues in my Linux install (I dual boot Windows 7 and Ubuntu from the same hard drive), and I can watch flash videos and play full 3D games with no latency or audio popping whatsoever, which leads me to think it is entirely a software issues, and is not down to faulty hardware.

Does anyone have any suggestions for further diagnosis, or even better, a resolution to this problem? It basically prevents me from gaming and having a decent multimedia platform.

OS: Windows 7 64-bit
CPU: Q6600 @ stock
Ram: 4GB
GPI: MSI 275GTX
MOBO: Gigabyte P35-DS3P
Net: PCI Realtek Ethernet NIC, no Wi-Fi hardware (on board ethernet broke a while ago, disappeared from device manager and from Linux)
Audio: Onboard Intel HDA
July 9, 2011 7:32:19 PM

How about getting a sound card? Maybe an Asus Xonar or Sound Blaster.
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July 10, 2011 1:28:31 AM

I could do that (I could also buy a new motherboard) but again, given that it seems to be a software issue, I'd rather try and rule out every other possible solution before I just spend money on new hardware, that gives me no guarantee that will actually fix the problem.

Thanks for the suggestion though :) 

It's probably also worth pointing out that I've tried a reformat and reinstall already, but the problem returns down the track (I only got a couple of weeks without problems)
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July 11, 2011 4:03:01 PM

Ok, a late night post after some tinkering, but I think I solved the problem.

I'm not entirely sure which exact step fixed it (I'll tinker a bit more tomorrow), but, after pursuing the line of enquiry regarding IRQ conflicts, I did two thinks in my BIOS. First, I disabled both my Serial and Parallel ports, and I also switched the PCI IRQ assignment from auto to manual, the first (I think was my NIC) to IRQ 4, and the second (which was my USB controller and another device, can't remember off the top of my head) to IRQ 7.

After booting into Windows, I now get no latencies longer than 208 microseconds at most. Before, I'd easily be reaching 16 000 regularly.
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October 22, 2013 8:19:25 PM

Hey, I was wondering how you changed these things. Im having the same problem, Im getting Latency that spikes red as high as LatencyMon goes. Ive reinstalled windows and flashed the BIOS back to the one it came with when I bought the laptop.I looked into Disabling Serial ports but I cant seem to find where to do that. Also I dont know what IRQ's n such my stuff runs on so I cant change that. (Tried winging it and had myself locked out of the computer until I did a power reset teehee oops)
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