System Resources

20.33 Hasyim Asyari 0 Comments

• System resources are shared between the different hardware components or devices of the computer system that need to communicate with CPU.
• The CPU is a complete computation engine that is fabricated on a single chip.
• It not only controls the functions of the computer, but also handles requests from many input and output devices.
• The CPU is only capable of handling one request at a time.

• Various hardware devices may want to tell the CPU that they have some information available that is ready for transfer. The devices indicate this by making an interrupt request, or IRQ.
• It is a general rule that IRQ’s cannot be shared.
• A device's IRQ will cause the operating system to stop momentarily as it asks the CPU to service its request.

• Direct Memory Access (DMA) channels allow devices to bypass the processor and directly access the computer memory.
• DMA channels are typically used by high-speed communication devices for transferring large amounts of data at high speeds.
• Examples include sound cards, some network cards, some SCSI cards, some disk drives, and some tape backup drives.

• An I/O port number is a memory address where data is temporarily stored as it moves in and out of the devices.
• The I/O address is very similar to a post office box. As mail comes in, it is stored temporarily in a post office box. No two boxes can have the same number or the mail can end up in the wrong box.
• No two devices can have the same I/O address.