A PCI device is any piece of computer hardware that plugs directly into a PCI slot on a computer’s motherboard. PCI, which stands for Peripheral Component Interconnect, was introduced to personal computers by the Intel Corporation in 1993.
The technology to operate PCI is integrated into the motherboard of nearly every personal computer manufactured since 1995. A PCI connection on a motherboard can be identified as a long strip of raised copper connectors encased in plastic. This long strip of connectors is usually called a bus.
The picture below shows an example of what PCI slots look like on a motherboard. As you can see, there are three PCI slots: PCI4, PCI5, and PCI6, as well as a CNR slot.
Examples of PCI device
- Network card
- Sound card
- Video card
- Wireless adapter
How many PCI slots are on a motherboard?
The number of PCI slots depend on the manufacturer and model of the motherboard on which a PCI device being installed. Today, very few motherboards come with any PCI slots as they have been replaced by PCI-E. Those motherboards that do come with PCI slots will generally have between one and three PCI slots. EVGA manufactures a somewhat deluxe motherboard with 7 PCIe slots.
What is a PCIe or PCI-E
Peripheral Component Interconnect Express (PCIe or PCI-E) is a serial expansion bus standard for connecting a computer to one or more peripheral devices.
PCIe provides lower latency and higher data transfer rates than parallel busses such as PCI and PCI-X. Every device that’s connected to a motherboard with a PCIe link has its own dedicated point-to-point connection.
This means that devices are not competing for bandwidth because they are not sharing the same bus.
What Do PCIe Slot Colors Mean?
By Dan Stone
Peripheral Component Interconnect slot colors are mostly aesthetic; the colors only mean something on advanced boards that use multiple slots for singular functions.
The Peripheral Component Interconnect Special Interest Group, or PCI-SIG, recommends that all PCI Express slots should be black, but does not require a specific color scheme. Many hardware manufacturers have taken up custom PCI Express coloring schemes to suit their motherboards because there is no slot color requirement.
Adding a PCI Device
- You open up your computer’s case and plug the sound card into an empty PCI slot on the motherboard.
Line up the contacts on the bottom of the PCI card with the PCI slot you plan to insert it into. Press the card firmly straight down into the slot. Ensure that the card is level and seated fully in the slot before continuing.
If you have the space, leave an open slot between your new card and any existing card. This will help keep your cards and components cooler.
Secure the card. Use the screw that you removed from the metal bay cover and use it to secure the card into the same hole. Tighten the screw firmly but not so tightly that it will strip later.
Your card will be suspended horizontally when you set your case back up, so securing it is very important.
- You close the computer’s case and power up the computer.
- The system BIOS initiates the PnP BIOS.
- The PnP BIOS scans the PCI bus for hardware. It does this by sending out a signal to any device connected to the bus, asking the pci device who it is.
- The sound card responds by identifying itself. The device ID is sent back across the bus to the BIOS.
- The PnP BIOS checks the ESCD to see if the configuration data for the sound card is already present. Since the sound card was just installed, there is no existing ESCD record for it.
- The PnP BIOS assigns IRQ, DMA, memory address and I/O settings to the sound card and saves the data in the ESCD.
- Windows boots up. It checks the ESCD and the PCI bus. The operating system detects that the sound card is a new device and displays a small window telling you that Windows has found new hardware and is determining what it is.
- In many cases, Windows will identify the device, find and load the necessary drivers, and you’ll be ready to go. If not, the “Found New Hardware Wizard” will open up. This will direct you to install drivers off of the disc that came with the sound card.
- Once the driver is installed, the device should be ready for use. Some devices may require that you restart the computer before you can use them. In our example, the sound card is immediately ready for use.
- You want to capture some audio from an external tape deck that you have plugged into the sound card. You set up the recording software that came with the sound card and begin to record.
- The audio comes into the sound card via an external audio connector. The sound card converts the analog signal to a digital signal.
- The digital audio data from the sound card is carried across the PCI bus to the bus controller. The controller determines which device on the PCI device has priority to send data to the CPU. It also checks to see if data is going directly to the CPU or to system memory.
- Since the sound card is in record mode, the bus controller assigns a high priority to the data coming from it and sends the sound card’s data over the bus bridge to the system bus.
- The system bus saves the data in system memory. Once the recording is complete, you can decide whether the data from the sound card is saved to a hard drive or retained in memory for additional processing.