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EISA-Bus Interrupts
The EISA bus supports 11 edge-triggerable or level-triggerable interrupts. IRQ0-IRQ2, IRQ8, and IRQ13 are used for internal functions only and are not available externally. The remaining 11 interrupt lines (IRQ3-IRQ7, IRQ9-IRQ12, IRQ14, IRQ15) are available for external system interrupts.
On Indigo2, all EISA interrupts are received at the same CPU level. When the CPU receives an EISA-bus interrupt, it responds to each device in IRQ priority order (lower number first). The operating system then determines which interrupt routine to use, based on the value specified by the device driver. Devices may share the same IRQ level.
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