PCI 2.2 allows for 66 MHz signaling (requires 3.3 volt signaling) (peak transfer rate of 266 MB/s)
PCI 2.3 permits use of 3.3 volt and universal keying, but does not allow 5 volt keyed add in cards.
Viac info mas na http://www.mindshare.com/protected/link.asp?id=50&s ection=43