This is machine that shows 24 IRQ channels. This machine belongs to one of my clients. ___________________________________________________ Machine Summary: OS Name Microsoft Windows XP Professional Version 5.1.2600 Service Pack 1 Build 2600 OS Manufacturer Microsoft Corporation System Name DELTA_MAIN_3 System Manufacturer To Be Filled By O.E.M. System Model To Be Filled By O.E.M. System Type X86-based PC Processor x86 Family 15 Model 2 Stepping 9 GenuineIntel ~2598 Mhz Processor x86 Family 15 Model 2 Stepping 9 GenuineIntel ~2598 Mhz BIOS Version/Date American Megatrends Inc. 1009.008, 03-07-21 SMBIOS Version 2.3 Windows Directory C:\WINDOWS System Directory C:\WINDOWS\System32 Boot Device \Device\HarddiskVolume1 Locale Canada Hardware Abstraction Layer Version = "5.1.2600.1106 (xpsp1.020828-1920)" User Name DELTA_MAIN_3\gerry Time Zone Eastern Daylight Time Total Physical Memory 1,024.00 MB Available Physical Memory 599.80 MB Total Virtual Memory 3.40 GB Available Virtual Memory 2.73 GB Page File Space 2.40 GB Page File C:\pagefile.sys __________________________________________________ This is the IRQ list on the machine that I am working on, extracted from System Information. IRQ 18 concerns me, with the sharing of one of the USB controllers and the Ultra ATA hard drive controler. Note that the display card is on IRQ 16, and is shared with 2 of USB Host Controllers. I am curious to know where 2, 3, 7, and 11 are in this system, and their use. IRQ 0 System timer OK IRQ 1 Standard 101/102-Key or Microsoft Natural PS/2 Keyboard OK IRQ 4 Communications Port (COM1) OK IRQ 6 Standard floppy disk controller OK IRQ 8 System CMOS/real time clock OK IRQ 9 Microsoft ACPI-Compliant System OK IRQ 10 Intel(R) 82801EB SMBus Controller - 24D3 OK IRQ 13 Numeric data processor OK IRQ 14 Primary IDE Channel OK IRQ 15 Secondary IDE Channel OK IRQ 16 ALL-IN-WONDER 9000 OK IRQ 16 Intel(R) 82801EB USB Universal Host Controller - 24D2 OK IRQ 16 Intel(R) 82801EB USB Universal Host Controller - 24DE OK IRQ 18 Intel(R) 82801EB USB Universal Host Controller - 24D7 OK IRQ 18 Intel(R) 82801EB Ultra ATA Storage Controllers OK IRQ 19 Intel(R) 82801EB USB Universal Host Controller - 24D4 OK IRQ 20 VIA OHCI Compliant IEEE 1394 Host Controller OK IRQ 21 Creative SB Audigy OK IRQ 21 Lava DSerial PCI PortA (COM4) OK IRQ 21 Lava DSerial PCI PortB (COM5) OK IRQ 22 3Com Gigabit LOM (3C940) OK IRQ 22 OHCI Compliant IEEE 1394 Host Controller OK IRQ 22 Standard Enhanced PCI to USB Host Controller OK IRQ 23 Standard Enhanced PCI to USB Host Controller OK IRQ 23 ALi PCI to USB Open Host Controller OK IRQ 23 U.S. Robotics V92 Fax PCI OK ________________________________________ Sharing: I/O Port 0x00000000-0x00000CF7 PCI bus I/O Port 0x00000000-0x00000CF7 Direct memory access controller I/O Port 0x000003C0-0x000003DF Intel(R) 82865G\PE\P Processor to AGP Controller - 2571 I/O Port 0x000003C0-0x000003DF ALL-IN-WONDER 9000 IRQ 21 Creative SB Audigy IRQ 21 Lava DSerial PCI PortA (COM4) IRQ 21 Lava DSerial PCI PortB (COM5) IRQ 22 3Com Gigabit LOM (3C940) IRQ 22 OHCI Compliant IEEE 1394 Host Controller IRQ 22 Standard Enhanced PCI to USB Host Controller IRQ 23 Standard Enhanced PCI to USB Host Controller IRQ 23 ALi PCI to USB Open Host Controller IRQ 23 U.S. Robotics V92 Fax PCI IRQ 16 ALL-IN-WONDER 9000 IRQ 16 Intel(R) 82801EB USB Universal Host Controller - 24D2 IRQ 16 Intel(R) 82801EB USB Universal Host Controller - 24DE IRQ 18 Intel(R) 82801EB USB Universal Host Controller - 24D7 IRQ 18 Intel(R) 82801EB Ultra ATA Storage Controllers Memory Address 0xA0000-0xBFFFF PCI bus Memory Address 0xA0000-0xBFFFF Intel(R) 82865G\PE\P Processor to AGP Controller - 2571 Memory Address 0xA0000-0xBFFFF ALL-IN-WONDER 9000 I/O Port 0x000003B0-0x000003BB Intel(R) 82865G\PE\P Processor to AGP Controller - 2571 I/O Port 0x000003B0-0x000003BB ALL-IN-WONDER 9000 I/O Port 0x0000C000-0x0000CFFF Intel(R) 82865G\PE\P Processor to AGP Controller - 2571 I/O Port 0x0000C000-0x0000CFFF ALL-IN-WONDER 9000 ______________________________________ -- Jerry G. ========================== This pertains more to win98 but may provide some help. There are 16 IRQs (15 usable) in a computer system. Here is a typical assignment of these IRQs: IRQ 0 System- System Timer IRQ 1 System- Keyboard IRQ 2 System- Cascadeable PIC (programmable interrupt controller), controls IRQ 8-15 IRQ 3 System- Serial Port (COM 2 and COM4) IRQ 4 System - Serial Port (COM 1 and COM3) IRQ 5 Available- General Adapter Use IRQ 6 System- Diskette Controller IRQ 7 System- Printer 1 IRQ 8 System- CMOS Real-time clock IRQ 9 Available- General Adapter Use IRQ 10 Available- General Adapter Use IRQ 11 Available- General Adapter Use IRQ 12 System- Mouse Port IRQ 13 System- Math Co-processor (even though this is built into the CPU, it still uses an IRQ) IRQ 14 System- Hard Disk Controller IRQ 15 Available- General Adapter Use As you can see, there are five (5) IRQs that are not assigned by the system design. Of these, one usually goes to the graphics card, one to the USB ports, and one to the modem. That leaves two (2) available IRQs for everything else. With care (and use of the proper cards), this is normally sufficient. Loading Sequence for Additional cards: First: Internal Modem (PCI) Second: Sound Card (PCI or ISA) Third: Network Card, a.k.a. NIC (PCI or ISA) Fourth: DVD Devices requiring Dxr3 Decoder Board (PCI) Note: Some video decoder boards require two (2) IRQs for complete functionality. Check with your video decoder card manufacturer for video decoder support and requirements. Fifth: SCSI Adapter (PCI) (This assumes that the system does not have a SCSI hard drive.) Sixth: Any others.
The additional IRQs are "virtual" IRQs, not true hardware IRQ lines. There are still only 16 actual hardware IRQ lines (0-15).
In Windows, peripheral component interconnect (PCI) devices can share IRQs. In accordance with the Plug and Play capability that is defined by the PCI specification, adapters are configured by the computer BIOS and are then examined by the operating system and changed if necessary. Typically, PCI devices have IRQs shared among them, especially on Advanced Configuration and Power Interface (ACPI) computers that have Windows ACPI support enabled. In Windows XP, Device Manager may list some or all the devices on your ACPI motherboard as using the same IRQ (IRQ 9). (To view the list of resources, click either Resources by type or Resources by connection on the View menu). No option is available to change the IRQ setting. Windows takes advantage of the ACPI features of the motherboard, including advanced PCI sharing. The PCI bus uses IRQ 9 for IRQ steering. With this feature, you can add more devices without IRQ conflicts. Further reading http://support.microsoft.com/default.aspx?scid=kb;EN-US;314068 You can check which device is connected to which USB port in Device Manager by right clicking on each instance of USB Root Hub, selecting Properties, then the Power tab. Any devices assigned will show up there.
