User`s guide

conga Tech Notes6

The conga-B915 has some technological features that require additional explanation. The following section will give the reader a better

understanding of some of these features. This information will also help to gain a better understanding of the information found in the System

Resources section of this user’s guide as well as some of the setup nodes found in the BIOS Setup Program description section.

Comparison of I/O APIC to 8259 PIC Interrupt mode6.1

I/O APIC (Advanced Programmable Interrupt controller) mode deals with interrupts differently than the 8259 PIC.

The method of interrupt transmission used by APIC mode is implemented by transmitting interrupts through the system bus and they are

handled without the requirement of the processor to perform an interrupt acknowledge cycle.

Another difference between I/O APIC and 8259 PIC is the way the interrupt numbers are prioritized. Unlike the 8259 PIC, the I/O APIC interrupt

priority is independent of the actual interrupt number.

A major advantage of the I/O APIC found in the chipset of the conga-B915 is that it’s able to provide more interrupts, a total of 24 to be exact.

It must be mentioned that the APIC is not supported by all operating systems. In order to utilize the APIC mode it must be enabled in the BIOS

setup program before the installation of the OS and it only functions in ACPI mode. You can nd more information about APIC in the IA-32 Intel

Architecture Software Developer’s Manual, Volume 3 in chapter 8.

Note

You must ensure that your operating system supports APIC mode in order to use it.

Native vs. Compatible IDE mode6.2

Compatible Mode6.2.1

When operating in compatible mode, the SATA and PATA (Parallel ATA) controller together need two legacy IRQs (14 and 15) and are unable

to share these IRQs with other devices. This is a result of the fact that the SATA and PATA controller emulate legacy IDE controllers.

Native 6.2.2

Native mode allows the SATA and PATA controllers to operate as true PCI devices and therefore do not need dedicated legacy resources, which

means it can be congured anywhere within the system. When either the SATA or PATA controller runs in native mode it only requires one PCI