System Resources
You should know the following facts about system resources.
IRQ (Interrupt Request):
• An IRQ allows a device to interrupt the CPU and request processing time.
• IRQ conflicts can cause random system lockups.
• On non-plug-and-play systems, each device requires its own IRQ. IRQs are usually set manually via jumpers or a programmable EEPROM on the device.
• On newer plug and play systems with the PCI expansion bus, devices can share IRQs.
• IRQ sharing is handled automatically by the operating system. For example, a USB port on a computer generally uses IRQ 9. However, you can connect up to 127 USB devices to that single USB port. Therefore, all devices using that port will also use IRQ 9.
• An IRQ for a plug-and-play device is set via the software driver installation program for that device.
• IRQs are assigned to devices in the following order:
o CMOS
o Hardware
o Software
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