System Resources, Interrupts, Apic Mode

System Support

4.3 System 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.

4.3.1 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, but may be inhibited by legacy hardware or software means external to the microprocessor.

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.

Most IRQs are routed through the I/O controller of the super I/O component, which provides the serializing function. A serialized interrupt stream is then routed to the ICH component.

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

■8259 mode

■APIC mode

These modes are described in the following subsections.

8259 Mode

The 8259 mode handles interrupts IRQ0-IRQ15 in the legacy (AT-system) method using

8259-equivalent logic. If more than one interrupt is pending, the highest priority (lowest number) is processed first.

APIC Mode

The Advanced Programmable Interrupt Controller (APIC) mode provides enhanced interrupt processing with the following advantages:

■Eliminates the processor's interrupt acknowledge cycle by using a separate (APIC) bus

■Programmable interrupt priority

■Additional interrupts (total of 24)

The APIC mode accommodates eight PCI interrupt signals (PIRQA-..PIRQH-) for use by PCI devices. The PCI interrupts are evenly distributed to minimize latency and wired as shown in Table 4-4.

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Technical Reference Guide

dc5850 specifications

The HP dc5850 is a desktop computer that was designed for business environments, offering a blend of performance, reliability, and efficiency. Released during the height of the mid-2000s, this system is powered by AMD processors, particularly the Athlon or Phenom series, which ensures that it can handle various computational tasks with ease.

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Graphics capabilities on the dc5850 are generally provided by integrated solutions, although users have the option to add discrete graphics cards for enhanced performance in visual tasks. The system often comes with integrated audio, which supports basic multimedia needs without requiring additional sound cards.

In terms of connectivity, the HP dc5850 features built-in Ethernet for wired networking and may also offer options for Wi-Fi capabilities via PCI expansion slots. This makes it suitable for networked business environments, enabling seamless integration into office infrastructures.

The system is designed with energy efficiency in mind, complying with various environmental standards, thereby reducing its carbon footprint. This aspect may also lead to lower operational costs for businesses focused on sustainability.

Overall, the HP dc5850 stands out as a versatile desktop solution, catering to the essential needs of small to medium-sized businesses. With its combination of performance, expandability, and energy efficiency, it remains a noteworthy choice for users seeking reliable computing power in a compact and manageable form.