3.3 Volt Supply on E2912A

E2912A adapters that where shipped after September '95, both the 5V and 3.3V pins are supplied. On adapters that where shipped before this date, the 3.3V pins (21a, 15b, 27a, 31b, 33a, 36b, 39a, 41b, 43b, 45a, 53a, 54b) are NOT bussed together (as required by the PCI specification) and 3.3V is not supplied to these pins nor is there a means to add this supply.Following are the relevant paragraphs out of the PCI specifcation Rev 2.1, which explain the technical background:4.3.4.1 - Power requirements (first paragraph, 3rd sentence)... Systems implementing the 5V signaling environment may either ship the 3.3V supply with the system or provide a means to add it afterwards (i.e. bus and decouple all 3.3V power pins) to support expansion boards that require it...However, concerning the 3.3V supply, the PCI specification Rev 2.1 says:4.3.4.1 - Power requirements (end of first paragraph) ... in the 5V signaling environment, an expansion card may not currently depend on 3.3V power being already available in the system. If a board used in that environment requires 3.3V power, it must provide its own power from a source on or associated with the expansion board, such as a voltage regulator, powered by either the 5V or 12V supplies.For clarification, here is a summary of the power pins on both the E2912A and E2914A:E2912A E2914A-------------------------------------------------------------------signaling environment +5V +3.3V+5V power pins +5V, bussed +5V, bussed+3.3V power pins not connected on OLD boards +3.3V, bussed+3.3V, bussed on NEW boardsV i/o pins +5V, bussed +3.3V, bussed-------------------------------------------------------------------