How to share a IRQ in your PC?

I\'ve problems installing new devices and components into my PC. I guess it\'s \'cause the pc is a little old. For example, I cannot print documents because my printer cannot be installed due to the system tell me I have not free IRQ port to use.

I know that IRQ ports can be shared among different devices, and I\'ve also some of them shared, but i dunno how to do it when the system request me for a free port.

Here you\'ve mi list of IRQs: (you can see that port 1 or 12 could be shared)

[Kurt Angle]

The printer port is normally called LPT1. On my computer is is set to IRQ 7 by default. I don\'t know how to change it though. I know on some computers you need to go into the bios and change some settings to activate the printer port.

On your settings I can see IRQ 14 and 15 look to be the same so maybe you could use on of those.

Good Luck

how are you hooking yer computer up?
parallel port?  usb?

Originally posted by mm
how are you hooking yer computer up?
parallel port?  usb?

You mean the printer mm? By parallel port.

Kurt they\'re the same in their name, but i dunno if they control the same devices. I cannot delete one of them without knowing the function of each one.

[§ôµÏG®ïñD]

If your comp is running in Apic mode, you can\'t change your IRQs. Unless you rip out your cards and re arrange em etc. Changing your comp into Pic mode will give u less irqs. but they tend to be far more stable.  By the looks of things your in pic mode. In bios you should be able to assign irqs to your pci slots. You should also be able to go into your systems device manager go to properties of what your want to change, then resources. Then you Should be able to change the IRQ.  Normaly your system should allow you to use the same irqs with no problems. Time to update.

actually, IRQ ports cannot be shared among different devices without causing problems in some way

they are interrupt requests (IRQ)

this is how hardware signals to the CPU that they need servicing

[§ôµÏG®ïñD]

Ahh, PnP should kick in anyway. Sharing the PCI Irqs without problems. Allowing the ports to have there own interrupts.

PNP?

the BIOS assigns IRQ\'s, not the OS (although the OS can override them whille it is running)

by default, the LPT (parallel port) is 7, and it seems yer soundblaster is bogart\'ing it

sharing IRQ\'s = headaches

[§ôµÏG®ïñD]

Setting up Bios for PNP OS enables your OS to control IRQ settings. Otherwise your Bios does. As soon as PNP OS is enabled in bios. Bios releases all control of IRQS to the OS. Unless your on linux, which doesn\'t really have any pnp support. Running your pc in Apic mode allows more IRQs but they tend to be very unstable. Running it in Pic mode gives u less IRQs but is far more stable.    Here\'s my system running in Pic mode with PNP enabled.

Now on a older OS and MB, you\'d probably get LOTS of errors.
I don\'t get any problems at all with IRQ sharing. I never get errors. On the Asus board i had i got nothing but problems.. Gigabyte rulez.

Thanx for helping guys.

The number of IRQs increases with the motherboard? I mean i\'ve right now 15 ports with my old board, there will be more in a modern one next year or the ports are always the same number?

[§ôµÏG®ïñD]

Ok, With old mbs they normally have 15 IRQs. The new mb support APIC mode which increases the IRQs.  I find Apic mode seems to be more unstable,
Apic = Advanced Programmable Interrupt Controller.
Pic = Programmable Interrupt controller.

Pic mode makes the PCI bus allow IRQs to be shared. For example, if there were only one IRQ left over after ISA devices were given their required IRQs, (each ISA device require 1 irq, they cannot share) all PCI devices could share it. In a PCI-only machine, there cannot be insufficient IRQs, as all can be shared.

APIC is a distributed set of devices that make up an interrupt controller. In current implementations, an APIC bus connects each part of a system. One part of the system, the "local APIC" delivers interrupts to a specific processor; for example, a machine with three processors must have three local APICs.  Pic mode IS NOT supported in multiple processor machines.

The other important part of the system is the I/O APIC. There can be as many as eight I/O APICs on a system; they collect interrupt signals from I/O devices and send messages to the local APICs when those devices need to interrupt. Each I/O APIC has an arbitrary number of interrupt inputs (or IRQs).

There\'s also Opic. Which i have no idea about.
 
Apic mode is very unstable on my machine. Sense the IRQs can be shared without any problems on pic mode in the latest machines. I prefer to use that.