PC Hacks

Hack #12. Manage Devices

Take control of device configuration.

One of the basic functions of the PC's BIOS is to identify and provide access to a variety of core components and I/O devices, whether they are embedded on the system board or plugged into an I/O card slot. Core components include the CPU, memory, internal system clocks and timers, and the I/O bus itself. Simple I/O devices supported by every BIOS include the keyboard, mouse, video adapter, I/O ports (serial, parallel, USB, and/or FireWire), and disk drive adapters. All of these devices have very predictable but limited places to be, including:

• Preset and expected hardware addresses (to access and get data to or from the device)

• Interrupt Request (IRQ) signals so devices can tell the CPU and programs they need attention

• Direct Memory Access (DMA) request and acknowledgment signals for devices and the CPU to communicate with each other, allowing high-speed data transfers directly to and from device memory

The earlier, or legacy, BIOS dealt with the hardware as provided, and the hardware configurations were preset or manually altered using switches and jumpers. When all you had were simple I/O devices, configuring a PC was manageable but admittedly not easy for those not inclined to get inside a PC and work with wires and jumpers. As PCs got more popular, more and more nontechnical users were exposed to them, and configuring a PC started to become a major frustration and technical support nightmare for PC vendors. As technology ...