3.3V, 5V and Universal PCI Issues

A "universal" PCI board is compatible with both 5V and 3.3V signaling environments. GSC's universal PCI boards detect the voltage provided on a dedicated PCI connector pin (VIO), and configure themselves automatically for the correct PCI bus logic levels. Although some confusion exists among users regarding the designation of a PCI board or slot as "3.3V," "5V" or "universal," all of these references should pertain to the PCI signaling levels (i.e.: logic levels), and not to a power requirement. To date (through Revision 2.3 of the PCI specification) all PCI-compliant bus configurations must provide all four power rails, i.e.: +5V, +3.3V and ±12V. Most GSC PCI based products use the +5V power rail as their primary source of power. These same products might be designated as "+5V-only" or "5V/3.3V" or "Universal," depending on their PCI logic level compatibilities. If the specification for a specific GSC PCI product does not explicitly specify universal signaling, contact GSC sales for clarification.