I have to say I think I’ve exhausted all the potential bottlenecks to try in my attempt to turn my MythTV box all-digital. The Avermedia A180 HDTV card simply doesn’t get along with my motherboard/CPU. I spent some time over the weekend adjusting the PCI latency times for the system’s peripherals, including removing and/or disabling unused devices. I also upgraded to the latest ivtv driver. These changes seemed to help: I was getting far more of the signal than I used to but I could never completely eliminate the dropped frames.
My tinkering did reveal that the CPU is only an Athlon 850 MHz when I thought it was at least a 1 GHz. That matters little as I place the blame on the bus speed or memory speed of the system. It just can’t keep up.
I also noted a conflict between the Avermedia A180 and the PVR-150 Plus. When the PVR-150 Plus is present the A180 will claim to be tuning channels but it won’t receive any signals. I read about this behavior with the PVR-150 and different card and it seems to be the same thing with the A180 and the PVR-150.
I don’t want to go back to the analog setup as I want to drop basic cable, but at this point its either that or invest in a new motherboard/CPU. I’ll come back to it some other time.