5V board in a 3.3V PCI slot

I am almost sure you don't have any 3.3V on your PCI Slot.

We have designed over 10 different PCI cards for different custom
projects based on our komodo board.
On the first prototyping board we were using both 5V and 3.3V from the
PCI Slot. Now all our new PCI boards use only 5V. Why? just because a
large part of motherboards *DO NOT PROVIDE* 3.3V on the PCI slots.

See our Komodo picture to find where is B side (slot side) and A side
(http://www.amontec.com/komodo.shtml )

You can verify your 3.3V on PCI finger pin no
B-25    B- for B side
B-31
B-36
B-41
B-43
B-54
A-21    A- for A side
A_27
A-33
A-39
A-45
A-53

Just take time to measure the voltage on one of these point !!!

Laurent Gauch
www.amontec.com
------------ And now a word from our sponsor ---------------------
For a secure high performance FTP using SSL/TLS encryption
upgrade to SurgeFTP
----  See http://netwinsite.com/sponsor/sponsor_surgeftp.htm ----

This varies with the type of PCI card you want to design.

The PCI spec says that 3.3V slots must provide both 3.3V and 5V power
supplies.  However, it also says that 5V slots do not have to provide
3.3V supply lines.  I've seen the odd motherboard with 5V slots which
had 3.3V supplies, but you are right they're rare.

So if you are designing either a 5V or a universal PCI card, it would
be a bad idea to use the 3.3V supply (other than VI/O).  But if you are
designing a 3.3V card, the 3.3V supply can be used.  Our customers are
telling us that it's getting harder and harder to find a server (non-
desktop) with 5V slots anymore.

      Steve
------------------------------------------------------------------------
Steve Schefter                         phone: +1 705 725 9999 x26
The Software Group Limited               fax: +1 705 725 9666
642 Welham Road,
Barrie, Ontario CANADA  L4N 9A1          Web: www.wanware.com

Hi Marco.



When a PCI card or slot is defined as 3.3V or 5V, it is describing the
voltage used for signalling (what voltage is used to drive the address/
data and control lines).  However, other voltages can be used as a
power source.  In particular, the PCI spec says that 3.3V slots must
also provide power on the 5V power supply lines.  This allows the
card to, for example, use 5V for the back end logic even though it talks
across the PCI bus at 3.3V.

The notch in the gold fingers only allow you to plug the correct type
of card (3.3V, 5V or universal) into the slot, so you don't have to
worry about that being wrong.

Having said that, I've seen at least one IBM server with 3.3V slots
which violated the PCI spec.  It didn't provide the 5V supply to the
PCI cards.  Checking the motherboard specs should resolve this though.

Regards,
       Steve
------------------------------------------------------------------------
Steve Schefter                         phone: +1 705 725 9999 x26
The Software Group Limited               fax: +1 705 725 9666
642 Welham Road,
Barrie, Ontario CANADA  L4N 9A1          Web: www.wanware.com