The Evolution of Resource Allocation
In the early days of personal computing, adding new hardware to a system was a task that often required technical expertise. Each device, from keyboards to modems, needed specific resources such as Interrupt Request (IRQ) lines, memory addresses, and Direct d https://bmmagazine.co.uk/ Memory Access (DMA) channels to function correctly. IRQ lines, for instance, are crucial as they signal the processor when a device requires attention. For example, every keystroke on a keyboard sends an IRQ to alert the processor.
The Challenge of Limited Resources
The system bus, a vital structure on the motherboard, facilitates communication between the processor, chipset, memory, and expansion slot devices. Initially, PCs utilized the Industry Standard Architecture (ISA) bus, which required manual setting of IRQs and other resources via jumpers or DIP switches on expansion cards. ISA devices could not share resources, meaning each needed its unique IRQ.
A typical PC only had 16 IRQs, which quickly became a limiting factor as more devices were added to systems. Standard devices like keyboards, mice, and drives had fixed resource assignments, as shown in the table below: