The PV-155 / PV-981-16 have four chipsets. Linux (and Windows) will only show / load four 'drivers'. Linux will show bttv0 - bttv3 in the kernel log (and also 'dmesg'). 

Linux users may need to specify this command as root: modprobe bttv card=77,77,77,77 
If you are using Zoneminder (and other Linux applications) you can access all of the 16 ports by this format:

/dev/video0
Channel: 0-3
/dev/video1
Channel: 0-3
/dev/video2
Channel: 0-3
/dev/video3
Channel: 0-3

Linux users may add the following to /etc/modprobe.conf so this command is run at startup: 
options bttv card=77,77,77,77 
See the Zoneminder FAQ / WIKI / Forums for more information
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