DPC (Deferred Procedure Calls)

Hello

First my self-built system specs:

A8N-SLI premium motherboard
2 x 1Go Corsair DDR C2
Athlon XP 3500+
Leadtek 6800 GS pci-e

I'm having exactly the same high DPC usage problem as everyone here, and as a lot of other people on other forums while googling the problem.

The common denominator so far seems to be either the nvidia nforce4 chipset or the nvidia 6800 GT / GS / ultra series GPU, as the problem is met across different MB and GC brands.

I'm categoric it isn't a spyware / software issue, but rather a driver / hardware one.

I myself have tried almost every driver combination, generic, modified, constructor, even older versions, be it for the chipset and for the gpu, starting almost everytime on a fresh Windows XP install, updated or not.

The high DPC usage seems to happen randomly. Often it occurs 10-20 mins now and then, sometimes it takes hours, and sometimes you are safe from it for a day or 2. It can start whenever. While gaming, surfing, doing nothing, but often right at the system boot or in the 10 coming minutes.

When happening, all system processes are ok, and idle process is taking 99% like usual, but the cpu usage graphs are reporting a 30-40% use, and sometimes even up to 100%. The comp is really becoming very sloppy, it isnt only a report error, the mouse is stuttering while moving, interaction and refreshing with the user interface gets delayed etc...

When checking it with process explorer, we can notice the high cpu usage is caused by an abnormal high hardware interrupts and defered procedure calls usage.

Another forumer tracked the driver causing that high dpc activity, and narrowed it down being videoport.sys (forgot the tool he used, might find it back if needed)

Without the video driver installed, the problem never occurs.

Like said before, changing those drivers didnt help either, being it nvidias generic ones, the constructor ones, or 3rd party modified ones, the problem remains.

I changed my videocard 2 times, for exactly the same brand / model (one standard exchange at my vendor, and one leaned by a friend)

Everytime it seemed to solve the problem... but after a week , the problem comes back. And once it's back, its back daily again....

Anyway, i'm clueless what to do now... no doubt if i put an ATI card or something else in it, it would work, maybe should i change the motherboard, but i'm convinced there is more behind it.

There are so many people having that exactly same problem, in particular with the 6800 GS, there might be some kind of incompatibility with the nforce4 chipsets or a driver problem, it can't be just coincidence.

i keep investigating.