One of my PCs is a MythTV backend, and the motherboard has enough PCI slots for my 2 pcHDTV OTA cards and a 1394 card used for importing/exporting Firewire DV to/from my camcorder.

I have one more PCI slot left but alas it is the one right beside the AGP slot, which to me has always been a no-no. I've always avoided using those PCI slots since they usually share an interrupt with the AGP slot on most bioses I've seen. If I've ever been forced to use it I've tried never to put a high-IO board there.

In this case, I've used the mobo's 2 SATA ports and am thinking of getting a SATA PCI card to support a SATA-type burner and maybe some more disks. I would not put that card beside the AGP slot. This would mean having to juggle the other cards and thus putting one of them into that slot beside the AGP.

The other option is shelling out for a Siig SC-UNS012 1394/SATA/USB2.0 combo card to replace the 1394 card I already have, but I'd rather not spend the money if I don't have to.

So, what are your experiences with using the side-by-side PCI/AGP slots together?

I have also avoided doing so due to the same reasoning.

On occasion, I have installed a card in there but I have not really paid too much attention to what the performance or stability is like. I have never had anything really bad happen though.

Sharing interrupts is not that big an issue these days. OTOH, I am a big believer in buying the "deluxe" motherboards than have firewire and extra USB/SATA ports on the motherboard. I have seen performance issues with sound cards but the slot doesn't seem to make much difference. PCI bandwidth appears to be a bigger issue, especially with real time data streams from/to drives, network devices and possibly firewire devices.

Its an Asus A8V mobo with 4GB ram and an Athlon X2 4200+ but the only thing missing from the mobo was 1394, thus the need for the card.

I torture-tested the system a while back by recording 2 simultaneous OTA HD streams while doing DV editing to/from my camcorder and there were no dropouts or issues.

Maybe I'll just have to torture-test it again with another IO board in that remaining slot and see what happens.

PCI bandwidth appears to be a bigger issue, especially with real time data streams from/to drives, network devices and possibly firewire devices.

Very true.

This is why PCI-E was created to do more than just replace AGP slots.

The biggest issue with PCI is that it is a shared bus that is set to the speed of the slowest card in the bus.

There are no (current) PCI-E versions of the pcHDTV cards on the market, so PCI it is...

I torture-tested the system a while back by recording 2 simultaneous OTA HD streams while doing DV editing to/from my camcorder and there were no dropouts or issues.

If your PCI bus is running in the best mode, you will have a fairly large amount of bandwidth to play with. About 252 MB/s to be precise. Or in another measurement, 2.1 gbps.

Hmmm.... the Siig combo card's specs say it maxes out at 150MB/sec so that might be a show stopper if I have to run Firewire and SATA through it (I would not be using its USB 2.0 capabilites since the mobo has plenty).