PCI

Case: You bought a NIC (PCI) 2.3 32-bit

Whereas your expansion slots are:

2 x PCI Express 2.0 x16 slots, support ATI CrossFireX™ technology at x8 link
(PCIe x16_1 blue, PCIe x16_2 black*)
3 x PCI Express x1 slots
2 x PCI slots
*PCI Express x16_2 slot (black at max. x8 link)

Knowledge database:

PCI is a computer bus for attaching hardware devices in a computer.

You can have a look at 32 bit PCI here or 64 bit PCI here.

Faster interfaces: PCI-X and PCI Express.

Conventional PCI remains a very common interface.

Have a look at A typical 32-bit PCI card( in this case a SCSI adapter from Adaptec) here

and A PCI-X Gigabit Ethernet expansion card here.

More information:

Conventional

• PCI 1.0, which was merely a component-level specification, was released on June 22, 1992.
• PCI 2.0, which was the first to establish standards for the connector and motherboard slot, was released on April 30, 1993.
• PCI 2.1 was released on June 1, 1995.
• PCI 2.2 allows for 66 MHz signalling at 3.3 volt signal voltage (peak transfer rate of 533MB/s), but at 33 MHz both 5 volt and 3.3 volt signal voltages are still allowed. Power rails to provide 3.3 volt supply voltage are now mandatory.^[3]
• PCI 2.3 permits use of 3.3 volt and universal keying, but does not allow 5 volt keyed add in cards.
• PCI 3.0 is the final official standard of the bus, completely removing 5-volt capability.
• Mini PCI is a form factor of PCI 2.2 for use mainly inside laptops
• CardBus is a PC card form factor for 32-bit, 33 MHz PCI
• CompactPCI uses Eurocard-sized modules plugged into a PCI backplane.
• PC/104-Plus is an industrial bus that uses the PCI signal lines with different connectors.

• PCI-X

  PCI-X is a high-performance variant of 64-bit PCI designed for servers.

  • PCI-X 1.0 increased the maximum signaling frequency to 133 MHz (peak transfer rate of 1066 MB/s) and revises the protocol.
  • PCI-X 2.0 permits a 266 MHz rate (peak transfer rate of 2133 MB/s) and also 533 MHz rate (4266 MB/s - 32x the original PCI bus), expands the configuration space to 4096 bytes, adds a 16-bit bus variant (allowing smaller slots where space is tight) and allows for 1.5 volt signaling
  • PCI-X adapters and slots are backward-compatible with 32-bit PCI slots and adapters.
  So it's not going to fit you motherboard!!!