HP D315 manual System Resources, Maskable Interrupts, Intr, Inta-..H

Chapter 4 System Support

4.4SYSTEM RESOURCES

This section describes the availability and basic control of major subsystems, otherwise known as resource allocation or simply “system resources.” System resources are provided on a priority basis through hardware interrupts and DMA requests and grants.

4.4.1 INTERRUPTS

The microprocessor uses two types of hardware interrupts; maskable and nonmaskable. A maskable interrupt can be enabled or disabled within the microprocessor by the use of the STI and CLI instructions. A nonmaskable interrupt cannot be masked off within the microprocessor, although it may be inhibited by hardware or software means external to the microprocessor.

4.4.1.1Maskable Interrupts

The maskable interrupt is a hardware-generated signal used by peripheral functions within the system to get the attention of the microprocessor. Peripheral functions produce a unique INTA-H (PCI) or IRQ0-15 (ISA) signal that is routed to interrupt processing logic that asserts the interrupt (INTR-) input to the microprocessor. The microprocessor halts execution to determine the source of the interrupt and then services the peripheral as appropriate.

Figure 4-9 shows the routing of PCI and ISA interrupts. Most IRQs are routed through the I/O controller, which contains a serializing function. A serialized interrupt stream is applied to the MCP component.

I/O & SM Functions

IRQ3..7, 9..12, 14,15

LPC47B367

I/O Cntlr.

Interrupt

Serializer

Serial IRQ

MCP

IDE IRQ14,15 Hard Drives

Interrupt

INTR-

Processor

PCI Peripherals

INTA-..H-

Processing

APIC bus

Figure 4-10.Maskable Interrupt Processing, Block Diagram

Interrupts may be processed in one of two modes (selectable through the F10 Setup utility):

♦8259 mode

♦APIC mode

4-14Compaq D315 and hp d325 Personal Computers Featuring the AMD Athlon XP Processor

Second Edition – April 2003