I've been through a few other threads on the same or a similar issue, but a few things are still unclear to me.  Rather than confuse one of the other threads by mixing in my scenario, I'll lay it out here:

The issue:

When recording from my Nvidia DualTV card, the feeds from the HD cards start breaking up, get choppy, etc.  It's not a signal strength issue.  I can turn it on and off by starting and stopping an NTSC recording, and checking the HD recording before and after the point in time that I start/stop.  While I can max out the CPU pretty easily, the problem manifests even with 30-50% CPU load.

Vista RTM

The hardware:

• Foxconn 6150K8MA-8EKRS motherboard
• Athlon 64 3000+
• 2GB RAM
• 7600 GT video
• 2 x AverMedia A180 HD Tuner cards
• Nvidia DualTV card
• 500GB drive (system and data partitions)
• DVD drive

I suspect it's IRQ related.

Both the video card (7600GT -- onboard video is disabled) and the DualTV card share IRQ 16.  Though no conflict is noted, in the critical sense, there may be a bottleneck there, since I'm sure that the video card is pretty busy...

The HD cards are on 17 and 18.

I have non-essential on-board devices disabled, leaving some gaps in the IRQ numbers available, but I'm not sure what range the BIOS and/or Vista will assign PCI resources to, so it's not clear if I'm stuck or not.  The motherboard documentation does not reference IRQ affinities per slot, but I'm hoping that with only the 3 PCI and 1 PCIe slot on the board, they don't have to share.  Though, for the sake of providing complete information, the card with the conflict is the the middle PCI slot.

This weekend, when I get time, I'm going to pull out all of the cards, reset the ESCD in BIOS, and see if adding the cards back it will redistribute the IRQ assignments.  Of course, if I just end up with another card sharing with video, or with another card, I'll just be moving to a different variation of the same problem.  Any suggestions on methodology?  Pull all cards, and start from on-board video?  Start with just the 7600GT, and add in cards one at a time?  One boot with just video, then all cards on a following boot?  Sacrifice a chicken?

Thanks,

--Mike

Nope, single core.  I'm thinking about upgrading, if for no other reason that to better support the streaming of content to my 360, but it doesn't appear as if the speed of the processor, or drivers for it (were it dual core), are the issue.

Since it's the recording itself, and not the playback, I thought that disk might be a bottleneck, but recording two HD streams works just fine, while one HD and one SD is an issue.

Thanks,

--Mike

I did a quick hardware shuffle, this morning, pulling all of the tuner cards, resetting the ESCD in BIOS, then adding the cards back (with Windows boots in between).

It looks like the middle PCI slot is tied to the same IRQ as the PCIe video card.  I also realized why the DualTV card is in the middle slot:  there are capacitors on the motherboard that block full, secure insertion of the card into the other two slots.  I was able to install the DualTV card in one of the other slots, anyway, at least for test purposes, and installed one of the A180 cards in another slot, leaving the middle, shared slot free.  The IRQ no longer shows as shared in Windows, but I can still repro the recording problem.  So, not an IRQ issue.

There are, and were, a number of other conflicts listed in the I/O resource category.  My next move will be a clean reinstall of the OS, starting with a clear ESCD and all cards installed.  My reasoning here is that if my original install was done with phased install of the cards, the system may not have been able to distribute resources that had already been assigned, or at least not do it well.  If all devices are present from the outset, perhaps I'll have better luck.

Otherwise, it's time to punt, and try to install at least some of the cards in my desktop machine (which only has 2 PCI slots).

Thanks,

--Mike

I have a little more research to do on this, but...

I found a reference to a known issue with the chipset on the DualTV:

(from a customer review of a card with the same chipset: http://www.newegg.com/Product/CustratingReview.asp?Item=N82E16815100012)

The VIXS XCODE-II chipset on this tuner does the PCI bus controlling and it causes a conflict with NForce based motherboards. This makes other devices on the PCI bus (DVICo, VBox, AverMeida A180 HDTV tuners) not work while the 500 is in use.

I had to pull the card to check (not listed in the literature), but that's the chipset the DualTV is using.

It looks like I'll have to see if there are other dual-tuner cards that do not experience this problem, and/or shift to a full ATX motherboard/case where I can fit four tuner cards.

Thanks,

--Mike

edit:  Quick search found at least one more reference.  Looks like I've found my problem.

http://www.htpcnews.com/forums/index.php?s=43d0851708f7ed0f78e8f49835c24d59&showtopic=22797&pid=167131&st=45&#entry167131