Originally posted by Thunderbird
Problems like this have existed in the past. It useally happens when the videocard and soundcard for some reason are sharing an irq. (especially with creative sblive cards ..)
Unfortunately not much drivers contain options to change the irq, so the only way is in various case to move cards to different slots. Perhaps it helps but first check if the cards are sharing an irq.
In both your cases it can also be the second pci videocard. The bandwith of the pci bus is limited and videocards consume lots of bandwith. (likely more when using the nvidia drivers instead of the nv because of more features and optimizations)
I already addressed every suggestion you made in what I originally wrote.
a) they are not sharing IRQs. detailed dmesg information upon request. Also, given that I've tried many ordering combinations, that also takes care of the possibility.
b) You can't change the IRQ of a PCI card without physically moving it. IRQ allocation on a PCI bus is hardwired.
c) The bandwidth of the PCI bus is much lower, yes, and that's exactly what the latency timer mechanism is for; to prevent one device from hogging the bus and driving latency-sensitive devices into starvation.
d) I tried four cards that were not SBLive variants, in fact, that were utterly unrelated to any chipset Creative ever used.
I appreciate the desire to help, but we're past the point of vague rules-of-thumb.