Basic PC Configuration Rules

The details of how the PC turned from a renegade project at IBM to a mega-industry go a long way toward explaining the limitations of the systems we have today. The basic PC configuration rules explain why even some new components consume both old and new resources.

The original IBM PC provided a meager hardware addressing range 400 bytes wide into which all the possible hardware (at the time) would exchange commands and data. In addition, eight interrupt request lines (IRQs) were available for hardware to signal the CPU and operating system that attention was needed. Further, it was anticipated that some devices would benefit from direct memory access (DMA) capabilities, and six channels were provided for that.