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End of Interactive Support
Intel is announcing the end of interactive support for the Intel® PR440FX Motherboard. See the End of Interactive Support Announcement for details.
The Intel® PR440FX Motherboard has a number of onboard devices that use IRQ resources. This can lead to a shortage of resources even though you may be using fewer add-in cards than you would with other motherboards. There are several ways to address this issue.
One method is to take advantage of the multiprocessing capabilities of the Intel PR440FX Motherboard and the added functionality this provides. The 820933AA I/O Advanced Programmable Interrupt Controller (IOAPIC) on the motherboard, when supported by an operating system which complies with Multiprocessor Specification version 1.4, provides additional IRQ capability that effectively presents additional IRQs to the system. This functionality virtually eliminates IRQ constraints.
Another method of addressing IRQ constraints is to take advantage of the capabilities of the PCI bus. According to the PCI Specification, revision 2.1, “PCI device drivers are required to support shared interrupts since it is very likely that system implementations will connect more than one device to a single interrupt line.” This means that PCI devices, with device drivers designed to conform to the PCI Specification, can share IRQs. This gives a system the capability of using more devices than the number of IRQs that are available.
If these suggestions do not solve your problem, you also might try:
- Disabling unused devices
- Moving PCI cards to different slots
These suggestions are detailed below.
There are often devices on the motherboard that are not being used. By disabling any unused devices on the motherboard, it may be possible to make resources available to other devices. When freeing resources in this manner, it may be necessary to clear the CMOS prior to changing settings in the BIOS Setup Utility. Clearing CMOS will erase any previous configuration information being stored in the ESCD region, and force the system to reconfigure from scratch.
It may also help to understand what resources are being shared among PCI devices. PCI devices are categorized as follows to specify their interrupt grouping:
- INTA: By default, all add-in cards that require only one interrupt are in this category. For almost all cards that require more than one interrupt, the first interrupt on the card is also classified as INTA.
- INTB: Generally, the second interrupt on add-in cards that require two or more interrupts is classified as INTB. (This is not an absolute requirement.)
- INTC and INTD: Generally, a third interrupt on add-in cards is classified as INTC and a fourth interrupt is classified as INTD.
The PIIX3 PCI-to-ISA bridge has four programmable interrupt request (PIRQ) input signals. Any PCI interrupt source (either onboard or from a PCI add-in card) connects to one of these PIRQ signals. Because there are only four signals, some PCI interrupt sources are mechanically tied together on the motherboard and, therefore, share the same interrupt. The table below lists the PIRQ signals and shows how the signals are connected to the PCI expansion slots and to onboard PCI interrupt sources.
| PCI Interrupt Routing Map for Intel PR440FX Motherboard |
| PIIX4 PIRQ Signal |
First
PCI Expansion Slot: J4D1 |
Second
PCI Expansion Slot: J4C1 |
Third
PCI Expansion Slot: J4B1 |
Fourth
PCI Expansion Slot: J4A2 |
USB |
LAN |
SCSI |
| PIRQ1 |
INTA |
INTD |
INTC |
INTB |
|
|
|
| PIRQ2 |
INTB |
INTA |
INTD |
INTC |
|
|
X |
| PIRQ3 |
INTC |
INTB |
INTA |
INTD |
|
X |
|
| PIRQ4 |
INTD |
INTC |
INTB |
INTA |
X |
|
|
By moving PCI cards to different slots, you may be able to configure the system in such a way that IRQs are distributed among the devices without conflicts. Again, you should clear the CMOS each time you attempt a new configuration to ensure that the system reallocates the resources from scratch.
For example, assume an add-in card which requires one interrupt (group INTA) is installed in the first PCI slot (J4D1). In this slot, an interrupt source from group INTA connects to the PIRQ1 signal, which is not connected to any onboard interrupt sources. If there are no other add-in cards, this card does not share its interrupt with any other devices.
Now, however, install a second add-in card that requires two interrupts (group INTA and INTB) into the fourth PCI slot (J4A2). INTA in the fourth slot is connected to signal PIRQ4 and INTB is connected to signal PIRQ1. Therefore, the second device on the two-function add-in card in the fourth slot will share its interrupt with the single-function card in the first slot. In addition, the first device on the two-function add-in card in the fourth slot will share its interrupt with the on-board USB controller.