Re: 5V System Environment / 3.3V System Environment in PCI s
3.3V PCI is rare, because the market is well-established with 5V cards.
You can interconnect 3.3V FPGA using MOSFET switches. There are chips designed to act as level cutter. They cut the 5V of PCI to 3.3V. On the other side, the 3.3V sent by the FPGA will pass through and end-up as 3.3V on PCI. This is still usually enough to drive most 5V PCI systems.
The design won't be PCI-complient (as per the specs) but will work in most systems, mainly because PCI specs tell that there shall be no intermediate chips between the PCI connector and the target chip, but the MOS gates are designed to have very low impact on the signals.
Plus, using the FET switches, you can design universal PCI cards.
Look at Xilinx app. notes XAPP646. This apply to Virtex-II FPGA, but is general for most FPGA.
**broken link removed**