Summary
Highlights
Computers are like digital cities, with various devices working in unison. Information transmission between components occurs through pathways called buses. Historically, components like the CPU and RAM were in separate cabinets, and information traveled between them via bundles of wires known as bus bars, which later became simply 'buses'.
The parallel bus uses multiple lanes (single wire connections) to transmit data. Data is broken into smaller pieces and sent simultaneously across these lanes. While effective, increasing the number of lanes for larger data sizes (e.g., 32-bit or 64-bit) makes the circuit physically larger. Multiplexers were introduced to divide data, sending it over fewer lanes across multiple clock cycles, improving processing while keeping devices compact. Parallel buses remain dominant for internal computer components like RAM and PCI-connected devices but may see decline.
A serial bus uses only one lane to transmit information, sending data one bit at a time. Initially slower and primarily used for long-distance communication due to lower cost, serial buses have improved in signal integrity and transmission speeds. They are now being adopted for short-range communication, previously reserved for parallel buses, and are found in connections like PCI Express, USB, and SATA.
The design of computer buses has evolved from bundles of wires to integrated connections within microprocessors and motherboards. Before the 1980s, a single 'system bus' connected major components, performing three functions: data transmission (data bus), locating addresses (address bus), and control operations (control bus). As integrated circuits shrunk, more efficient bus architectures emerged, though the system bus can still be found in embedded systems.
By the mid-1980s, CPUs used the Northbridge and Southbridge (chipset) to communicate with components. The Northbridge, connected directly to the CPU by the Frontside Bus (FSB), managed high-priority components like RAM and video cards. The Southbridge handled slower, lower-priority connections such as USB, SATA, and Ethernet, connecting to the Northbridge via an internal bus. This arrangement made systems more efficient and faster.
Buses are crucial for computers, creating a unified environment for components to function as one. As systems continue to evolve, so too will bus architecture, adapting to new technological demands and ensuring efficient data flow.