(125points) Manually Configuring IRQs under XP

Posted on 2004-09-11
Last Modified: 2008-03-10

I'll start by telling you that you may use all the tech-terms you want, no problem. I've been using computers since 92 and am not afraid of difficult solutions.

The problem I'm currently having is due to XP's automatic resource assignment. XP uses a new formula, "don't rebalance IRQs even if need be, it's too "risky"". "Risky" being a word taken from the MSDN entry for how IRQ assignment works on XP. This means that IRQs stay once they've been assigned.

[Note: There is one "solution" that I don't want to hear from. You can change the HAL from "ACPI" to "Standard PC". However, Microsoft clearly states that doing so WILL create an instable system. The reason being that several drivers required for "Standard PC" are not installed (they are only installed when choosing "Standard PC" during XP setup), and you'll still have leftovers from the "ACPI" HAL. So please, no comments about how I should change the HAL to "Standard PC", it's critical that this computer is able to run 24/7.]


Moving on to the problem. I have 3 VERY high-bandwidth devices sharing IRQ 10. Namely:

- Radeon 9600 XT [graphics]
- PDI Deluxe [professional video capture card (rgb), immense bandwidth requirement]
- Pinnacle PCTV [tv tuner, used to watch TV on your computer]

The latter (PCTV) is able to co-exist with the Radeon. While the Radeon recieves and outputs graphics, the PCTV can happily capture video at the same time. The PCTV video stream is compressed and not high-bandwidth.

However, if I start capturing RGB-video using the PDI Deluxe, the bandwidth is far from enough. The bus drops 10 captured frames per second due to overload (resulting in jerky motion).
After a while the graphic card locks up due to dropped data that SHOULD have reached the Radeon if not the bus had been so overloaded.
"ATI VPU Recover" sometimes manages to reinitialize and save the card so that I get enough visual feedback for a reboot.

The CPU load never goes above 50% and there is no real heat in the system so those two can be ruled out. I definitely believe that the IRQ sharing for these devices, sending extremely high-bandwidth data back and forth simultaneously over the same channel (IRQ 10), is causing the problems.


I need to solve this before monday as I'll be needing the video capture at a conference. My question is, what can I do to spread the IRQs? I am using Windows XP Professional (English).

Steps taken so far:
* I tried to free up some IRQs by disabling the COM ports and LPT port, which gave me 3 new IRQs. But as mentioned above (from MSDN), Windows XP does not rebalance IRQs even if you free up some more.
* Googled for a few hours.
* I'd like to keep the card structure in the box (not move them around unless it's not possible to fix this software-wise). The reason being that this is a HTPC (Home theater PC) where cards are arranged in this order: Audio Out (5.1), Audio In (24/96), Video In (PDI Deluxe), TV In (PCTV), Video Out (Radeon) with a printed label that would have to be completely redone.

Best Regards,
Christopher Hilding
CEO Pulseforce
Question by:pulseforce
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Accepted Solution

ashishdaga earned 125 total points
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Thanks. Well, that's the MSDN entry I read. And I've already read that thread and tried everything.

Just now I went into the BIOS and set all but 5 IRQs to "Reserved", and disabled "assign irq for USB". But Windows XP ignored it and still keeps all devices on IRQ 10.

I then booted into windows and went to the video capture program, and almost instantly (10 seconds) after starting the rgb capture, the Radeon crashed. It was recovered by ATI VPU Recover but then crashed again since the video card (PDI Deluxe) was still capturing. This time it could not be saved.

This is a SERIOUS issue. Can't I get windows XP to reassign all IRQs somehow?

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Sorry, by "keeps all devices on IRQ 10" I mean those 3 (ati radeon, pdi deluxe, pinnacle pctv). I don't want to cause confusion.

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The IRQ has now been reassigned, and the PDI Deluxe is alone on IRQ 5.

But I am STILL having the dropped frames and the final death of the graphics card requiring a cold reboot.

I believe that it's the PCI Bandwidth that is insufficient then. Because my second video capture card sends lower-bandwidth, compressed video and works properly. But the PDI Deluxe sends uncompressed RGB, just as the Radeon does. Therefore I think this may be causing overload leading to dropped frames in the video capture, and then a lockup of the graphics card due to dropped data.

What is your take on this?

Motherboard: SOYO P4S-645DX Dragon Ultra.
It is SiS 645DX-based, so it's not Intel.

I have not found a definite answer when searching google, just hints that this motherboard may have insufficient bandwidth to drive the PDI Deluxe.

In addition, the PDI Deluxe manufacturer wrote this in the forum: "A case was reported by a combo user that a P4 SiS 648 mainboard caused video stuttering problem. Now the user is using an Intel chipset mainboard and no more stuttering is observed."

This is my first symptom, stuttering due to dropped frames, and then the graphics card dies. Could this be related? Is the PCI Bandwidth insufficient?

I'm lost. Should I try to get another, Intel-based motherboard?
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I decided to pursue a new motherboard and I wrote a thread at the PDI Deluxe-forum that contains the requirements at the bottom.

The foremost requirement is APIC (Advanced Programmable Interrupt Controller) support!

God Bless,
Christopher H.

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Even though ashishdaga didn't actually help (I knew about both pages), he will get the points. Reason being that it's been solved, I am getting a new mainboard.

The company I bought this SiS board from was pretty scared when I confronted them and demanded to swap it for an Intel-based chipset,

Their answer was that they put this board up by "accident", and that they "luckily" sold only 17 of them. My guess is that they wanted to get rid of them since they are basically really, really bad and faulty straight from the factory.

<B>Stay away from SiS!</B>

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Thanks for the advise Chris. Will stay away from SIS. All the best with the new motherboard.

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Thanks ashishdaga,

I'm getting an Asus P4C800-E Deluxe, using the top-of-the-line Intel 875P chipset. I know that I can't go wrong, several people dealing with video capture recommended it to me.

Take care,


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