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RE: PCI 5V board
- To: Mailing List Recipients <email@example.com>
- Subject: RE: PCI 5V board
- From: "Ingraham, Andrew" <Andrew.Ingraham@compaq.com>
- Date: Thu, 24 Jun 1999 08:18:06 -0400
- Cc: "'pci-sig'" <firstname.lastname@example.org>
- Delivered-To: pcisig@teleport.COM
- Resent-Date: Thu, 24 Jun 1999 05:58:33 -0700
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- Resent-Message-ID: <"4lAkW1.0.sK7.IGYSt"@electra.znyx.com>
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>Does the 5V board connectors have to support +3.3V Pinout?
>If not, does they have to be not connected ? or they can have different
>voltage (some of them 3.3V and some 5V)?
>Can I connect them together?
In the current PCI spec (rev 2.2), +5V, +3.3V, +12V, and -12V all must be
supplied from the system (motherboard) to all PCI connectors, whether the
bus uses 5V signaling or 3.3V signaling.
For the old spec, rev 2.1, a bus with 5V signaling could have omitted the
+3.3V power source as long as there was a provision for adding one later.
Thus, all +3.3V pins had to be wired up, decoupled, and ready for +3.3V.
PCI bus pins should never be used for any other purpose.
On PCI expansion cards, power pins should be connected and decoupled,
whether or not that supply voltage is used by the card.