Introduction to Motherboard Buses
- A motherboard resembles a small city with interconnected components.
- The computer bus is the pathway that connects different motherboard components,
enabling communication.
- Examples of buses include:
- The bus connecting memory slots to the CPU.
- The bus connecting expansion slots.
- Buses allow diverse components to function as a single unit and enable
expandability (e.g., adding expansion cards).
- Physical traces on the motherboard represent these buses, which can be traced from one component to
another.
PCI (Peripheral Component Interconnect) Bus
- Introduced in 1994, PCI is an older bus standard.
- Uses parallel communication, sending multiple bits simultaneously.
- Two variants:
- 32-bit PCI: 32 separate connections for sending 32 bits at once.
- 64-bit PCI: 64 separate connections for sending 64 bits at once.
- Expansion cards plug into PCI slots, which have small tabs or keys
to designate power settings.
- A 64-bit PCI card has additional connectors and a separate keyway for
identification.
- Installation involves aligning the card with the slot and pressing firmly (avoid excessive force).
- Once installed, the card is secured to the case with a screw to prevent accidental removal.
PCI Express (PCIe) Bus
- A modern bus standard using serial communication (one bit at a time).
- More efficient than PCI’s parallel communication.
- Uses lanes for data transfer:
- PCIe x1: 1 lane (pronounced "by one").
- PCIe x2, x4, x8, x16: Multiple lanes for increased throughput.
- Each lane consists of two pathways: one for sending and one for receiving data.
- Physical differences from PCI:
- Keyway is closer to the edge of the motherboard.
- Smaller slots for lower-lane configurations (e.g., PCIe x1).
- Some cards have a latch mechanism for additional security.
- Removal requires unlatching the card in addition to unscrewing it from the case.
Comparing PCI and PCIe
- Both may appear on the same motherboard but serve different purposes.
- Key differences:
- PCI: Parallel communication, wider slots, keyway further from the edge.
- PCIe: Serial communication, scalable lanes, keyway closer to the edge.
- PCIe is the standard for modern systems due to higher efficiency and scalability.