PCI and PCI-X Voltage and Interchangeability

[mrfrustrated]

Main Question:
Will a card with "Connector Type(s) 1 - PCI / PCI-X (Universal 3.3 & 5V; 32-bit)," be compatible in a PCI-X 64/100 3.3v slot or PCI-64/66 3.3v slot on my motherboard? This card has both 3.3v and 5v tab on the connector.

Since the PCI-X and PCI-66 slots are only 3.3v will the card be underpowered? 

Can I plug in the 3.3v end in to the smaller notch on either PCI-66 or PCI-X slot and since the 5v end is not plugged into the smaller notch the card and board will not overheat?    

*This card: http://www.startech.com/Cards-Adapters/USB-3.0/Cards/4-Port-PCI-SuperSpeed-USB-3-Adapter-Card-with-SATA-SP4-Power~PCIUSB3S4

*This Server Board: ftp://ftp.dell.com/Manuals/all-products/esuprt_ser_stor_net/esuprt_poweredge/poweredge-1600sc_Reference%20Guide_en-us.pdf

---Board Page 4
---Expansion Slots Page 68
**Yes I have already used all the Conventional PCI 32/33 slots

Additional Questions: (I need a better understanding) 
I have read I can use Conventional PCI cards on the PCI-X slot is this also true for the PCI-66 slot?

If Conventional PCI cards are backwards compatible on my other PCI-X and PCI-66 slots will I have a voltage issue using a 5v card in a 3.3v PCI slot?

Thanks a bunch,
-Mr. Frustrated   

[Computer_Commando]

PCI-X is now obsolete.  Your motherboard has 4 of these.
http://en.wikipedia.org/wiki/PCI-X


The USB3.0 PCI card you have referenced may work in any of the 6 slots.  Tech specs say it's PCI-X compatible, so you would want to use it in one of the 4 because it might be faster.
http://www.startech.com/Cards-Adapters/USB-3.0/Cards/4-Port-PCI-SuperSpeed-USB-3-Adapter-Card-with-SATA-SP4-Power~PCIUSB3S4
The Startech PCI-USB3.0 is the only one made that has a PCI interface, all others are PCI-e.


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