This occurs in FreeBSD 3.x with PCI sound cards. The pcm0 device is reserved exclusively for ISA-based cards so, if you have a PCI card, then you will see this error, and your card will appear as pcm1.
Note: You cannot remove the warning by simply changing the line in the kernel config file to device pcm1 as this will result in pcm1 being reserved for ISA cards and your PCI card being found as pcm2 (along with the warning ``pcm1 not found'').
# cd /dev # ./MAKEDEV snd1
This situation does not arise in FreeBSD 4.x as a lot of work has been done to make it more PnP-centric and the pcm0 device is no longer reserved exclusively for ISA cards